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Prescriptive methods have been at the core of modern hearing aid fittings for the past several decades. Every decade or so, there have been revisions to existing methods and/or the emergence of new methods that become widely used. In 2001 Byrne et al provided a comparison of insertion gain for generic prescriptive methods available at that time.
The purpose of this article was to compare National Acoustic Laboratories-Non-linear 1 (NAL-NL1), National Acoustic Laboratories-Non-linear 2 (NAL-NL2), Desired Sensation Level Multistage Input/Output (DSL m[i/o]), and Cambridge Method for Loudness Equalization 2-High-Frequency (CAMEQ2-HF) prescriptive methods for adults on the amplification characteristics of prescribed insertion gain and compression ratio. Following the differences observed in prescribed insertion gain among the four prescriptive methods, analyses of predicted specific loudness, overall loudness, and bandwidth of cochlear excitation and effective audibility as well as speech intelligibility of the international long-term average speech spectrum (ILTASS) at an average conversational input level were completed. These analyses allow for the discussion of similarities and differences among the present-day prescriptive methods.
The impact of insertion gain differences among the methods is examined for seven hypothetical hearing loss configurations using models of loudness perception and speech intelligibility.
Hearing loss configurations for adults of various types and degrees were selected, five of which represent sensorineural impairment and were used by Byrne et al; the other two hearing losses provide an example of mixed and conductive impairment.
Prescribed insertion gain data were calculated in 1/3-octave frequency bands for each of the seven hearing losses from the software application of each prescriptive method over multiple input levels. The insertion gain data along with a diffuse field-to-eardrum transfer function were used to calculate output levels at the eardrums of the hypothetical listeners. Levels of hearing loss and output were then used in the Moore and Glasberg loudness model and the ANSI S3.5-1997 Speech Intelligibility Index model.
NAL-NL2 and DSL m[i/o] provided comparable overall loudness of approximately 8 sones for the five sensorineural hearing losses for a 65 dB SPL ILTASS input. This loudness was notably less than that perceived by a normal-hearing person for the same input signal, 18.6 sones. NAL-NL2 and DSL m[i/o] also provided comparable predicted speech intelligibility in quiet and noise. CAMEQ2-HF provided a greater average loudness, similar to NAL-NL1, with more high-frequency bandwidth but no significant improvement to predicted speech intelligibility.
Definite variation in prescribed insertion gain was present among the prescriptive methods. These differences when averaged across the hearing losses were, by and large, negligible with regard to predicted speech intelligibility at normal conversational speech levels. With regard to loudness, DSL m[i/o] and NAL-NL2 provided the least overall loudness, followed by CAMEQ2-HF and NAL-NL1 providing the most loudness. CAMEQ2-HF provided the most audibility at high frequencies; even so, the audibility became less effective for improving speech intelligibility as hearing loss severity increased.
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... To achieve this, a speech intelligibility model, based on a modified version of the Speech Intelligibility Index (ANSI 1997), was combined with a loudness model (Moore & Glasberg 2004) in an adaptive computer-controlled optimization process. The Speech Intelligibility Index model was modified by introduction of an "effective audibility factor," which takes into account the finding that, as the hearing loss gets more severe, less information is extracted from the speech signal even when the speech signal is above the detection threshold (Ching et al. 1998Turner & Cummings 1999;Johnson & Dillon 2011;Keidser et al. 2011). In addition, empirical data on the loudness and quality of sounds amplified according to the NAL-NL1 prescription were taken into account (Smeds et al. 2006;Keidser et al. 2007Keidser et al. , 2008. ...
... In addition, empirical data on the loudness and quality of sounds amplified according to the NAL-NL1 prescription were taken into account (Smeds et al. 2006;Keidser et al. 2007Keidser et al. , 2008. NAL-NL2 recommends less mid-frequency gain and more low-and high-frequency gain than NAL-NL1 does (Johnson & Dillon 2011). NAL-NL2 recommends gain for frequencies up to 8 kHz, whereas the limit for NAL-NL1 is 6 kHz. ...
... It is clear that for speech with medium and low levels, CAM2 leads to markedly higher audibility at medium and high frequencies than NAL-NL2 does, consistent with the analysis of Johnson and Dillon (2011). ...
To compare preference judgments for sounds processed via a simulated five-channel compression hearing aid with gains and compression ratios selected according to two recently introduced fitting methods, CAMEQ2-HF (hereafter named CAM2) and NAL-NL2.
There were 15 participants with sloping sensorineural hearing loss. They had mild losses, typical of people who might be candidates for wide-bandwidth hearing aids. Within a given trial, the same segment of sound was presented twice in succession to one ear, once with CAM2 settings and once with NAL-NL2 settings, in random order. The participant had to indicate which one was preferred and by how much. Judgments of overall sound quality were obtained for female and male speech in quiet and for four types of music (classical, jazz, a man singing, and percussion). Judgments of speech clarity were obtained for female and male speech in speech-shaped noise, female speech in a male-talker background, and male speech in a female-talker background. Factors investigated included compression speed (slow or fast) and input sound level (50, 65, or 80 dB SPL).
The pattern of the results was reasonably consistent across participants, but the magnitude of the effects was small. For judgments of overall sound quality, nine participants preferred CAM2 relative to NAL-NL2, and the remainder showed no clear preference. There was a significant overall preference for CAM2. The preference for CAM2 over NAL-NL2 in overall sound quality was present for all types of stimuli, both compression speeds, and all three levels. For judgments of the clarity of speech in noise, five participants preferred CAM2 over NAL-NL2, one showed the opposite preference, and the remainder showed no clear preference. There was a significant overall preference for CAM2. The preference for CAM2 over NAL-NL2 in the context of clarity of speech in noise was present for all types of stimuli, both compression speeds, and all three levels. For judgments of the clarity of speech in a background talker, CAM2 was significantly preferred overall relative to NAL-NL2, but the effect was very small.
For participants with mild sloping hearing loss, a simulated hearing aid unilaterally fitted using CAM2 was preferred over the same aid fitted using NAL-NL2 for overall sound quality and the clarity of speech in noise. Preferences differed only very slightly for the clarity of speech in a background talker. Further work is needed to establish whether similar preferences would be found in everyday life.
... As versões anteriores destas prescrições genéricas diferiam muito no ganho prescrito, com a DSL v4 prescrevendo substancialmente mais ganho do que a NAL-NL1. A última versão das duas prescrições tornou-se muito mais semelhante (19) , principalmente porque a DSL v5.0a prescreve substancialmente menos ganho do que DSL v4 para adultos usuários de AASI (17) . ...
... Dworsack-Dodge (7) demonstrou semelhança entre as prescrições dos métodos nas frequências médias e divergências nas extremidades de frequência para um nível de entrada de 65 dB NPS, com a NAL-NL2 fornecendo mais ganho em frequências baixas e menos ganho em frequências altas em relação à DSL v5.0a. Já o estudo de Johnson e Dillon (19) avaliou o impacto das diferenças de ganho de inserção entre alguns métodos prescritivos para diferentes configurações hipotéticas de perda auditiva considerando indivíduos adultos. Na comparação, a DSL v5.0a prescreveu menor ganho nas frequências médias e baixas até 4000 Hz e maior ganho em 6000 e 8000 Hz do que a NAL-NL2 para audiogramas representando perdas sensorioneurais de configurações variadas. ...
... Porém, devido à variabilidade na acústica da fala em diferentes situações de audição, o SII pode superestimar ou subestimar a audibilidade. Estudos recentes demonstraram que valores semelhantes de SII podem resultar em níveis muito diferentes de compreensão de fala dependendo de quais bandas de frequência são audíveis para o ouvinte (19,26) . ...
To comparatively analyze the NAL-NL2 and DSL v5.0a prescriptive methods according to the hearing aids individualized programming for the elderly with hearing loss.
The study included 60 elderly individuals with hearing loss, who underwent RECD (Real Ear to Coupler Difference) measurement and hearing aids individualized programming by NAL-NL2 and DSL v5.0a prescriptive methods. The performance verification for each prescription was performed using REAR measurements (Real Ear Aided Response), SII calculation (Speech Intelligibility Index) and HINT (Hearing In Noise Test). The comparative statistical analysis was performed using the paired t-test.
The NAL-NL2 method presented a better performance in the REAR evaluation in low and high frequency bands for medium and loud intensity input sounds, in the high frequency range for low intensity input sounds, and in the SII calculation for soft input sounds. The DSL v5.0a presented better results in the REAR evaluation in medium frequencies for medium input sounds, in low and medium frequencies for soft input sounds, in the SII calculation for medium and loud input sound, and in the HINT test in silent and noisy situations.
The findings of this study point to an equivalent performance between the DSL v5.0a and NAL-NL2 procedures in the adaptation of hearing aids in the elderly with hearing loss. The amplification calculated by DSL v5.0a provided better speech perception in silence.
... Practitioners have generally been cautious about basing amplification parameters on patient preference; that is, preferred amplification parameters for highly regarded sound quality are not necessarily the ones that lead to optimal performance on the dimension of speech intelligibility (Logan et al, 1984;Harris and Goldstein, 1985). Albeit including patient preferences is an integral part of the clinic service delivery model encouraging an interactive and patient-driven, practitioner-facilitated exchange, a patient is also intuitively much more likely to wear a hearing aid with the amplification parameters he or she prefers (e.g., Humes and Hackett, 1986;Smeds et al, 2006aSmeds et al, , 2006bJohnson and Dillon, 2011). ...
... Prescriptive approaches for hearing aids have thus been careful to recommend amplification gain with consideration to predicted speech intelligibility and/or loudness (Rankovic, 1991;Cornelisse et al, 1995;Cox, 1995;Byrne et al, 2001;Keidser et al, 2011). Johnson and Dillon (2011) reported on four prominent generic hearing aid prescriptions indicating that all were comparable with regard to predicted speech intelligibility but did differ markedly in terms of predicted loudness. The Johnson and Dillon (2011) study focused on generic prescriptive procedures because they are not specific to, and may be used with, any brand or product model of hearing aid. ...
... Johnson and Dillon (2011) reported on four prominent generic hearing aid prescriptions indicating that all were comparable with regard to predicted speech intelligibility but did differ markedly in terms of predicted loudness. The Johnson and Dillon (2011) study focused on generic prescriptive procedures because they are not specific to, and may be used with, any brand or product model of hearing aid. ...
Johnson and Dillon (2011) provided a model-based comparison of current generic hearing aid prescriptive methods for adults with hearing loss based on the attributes of speech intelligibility, loudness, and bandwidth.
This study compared the National Acoustic Laboratories-Non-linear 2 (NAL-NL2) and Cambridge Method for Loudness Equalization 2-High-Frequency (CAM2) prescriptive methods using adult participants with less high-frequency hearing loss than Johnson and Dillon (2011). Of study interest was quantification of prescribed audibility, speech intelligibility, and loudness. The preferences of participants for either NAL-NL2 or CAM2 and preferred deviations from prescribed settings are also reported.
Using a single-blind, counter-balanced, randomized design, preference judgments for the prescriptive methods with regard to sound quality of speech and music stimuli were obtained. Preferred gain adjustments from the prescription within the 4-10 kHz frequency range were also obtained from each participant. Speech intelligibility and loudness model calculations were completed on the prescribed and adjusted amplification.
Fourteen male Veterans, whose average age was 65 yr and whose hearing sensitivity averaged normal to borderline normal through 1000 Hz sloping to a moderately severe sensorineural loss, served as participants.
Data collection and analysis:
Following a brief listening time (~10 min), typical of an initial fitting visit, the participants made paired comparison of sound quality between the NAL-NL2 and CAM2 prescriptive settings. Participants were also asked to modify each prescription in the range of 4-10 kHz using an overall gain control and make subsequent comparisons of sound quality preference between prescriptive and adjusted settings. Participant preferences were examined with respect to quantitative analysis of loudness modeling, speech intelligibility modeling, and measured high-frequency bandwidth audibility.
Consistent with the lack of difference in predicted speech intelligibility between the two prescriptions, sound quality preferences on the basis of clarity were split across participants while some participants did not have a discernable preference. Considering sound quality judgments of pleasantness, the majority of participants preferred the sound quality of the NAL-NL2 (8 of 14) prescription instead of the CAM2 prescription (2 of 14). Four of the 14 participants showed no preference on the basis of pleasantness for either prescription. Individual subject preferences were supported by loudness modeling that indicated NAL-NL2 was the softer of the two prescriptions and CAM2 was the louder. CAM2 did provide more audibility to the higher frequencies (5-8 kHz) than NAL-NL2. Participants turned the 4-10 kHz gain recommendation of CAM2 lower, on average, by a significant amount of 4 dB when making adjustments while no significant adjustment was made to the initial NAL-NL2 recommendation.
NAL-NL2 prescribed gains were more often preferred at the initial fitting by the majority of participating veterans. For those patients with preference for a louder fitting than NAL-NL2, CAM2 is a good alternative. When the participant adjustment from the prescription between 4 and 10 kHz exceeded 4 dB from either NAL-NL2 (2 of 14) or CAM2 (11 of 14), the participants demonstrated a later preference for that adjustment 69% of the time. These findings are viewed as limited evidence that some individuals may have a preference for high-frequency gain that differs from the starting prescription.
... A sampling study of other prominent generic prescriptive techniques (i.e., Johnson and Dillon, 2011) indicated that DSL m[i/o] provided much less insertion gain than CAM2 or NAL-NL2 for hearing losses containing a conductive component. One possible reason may be continued usage of an AC threshold plus 25% of the ABG approach based on the following statements from Scollie et al (2005): ...
... (p. 190) The CAM2 prescriptive method appeared to use near 100% restoration of the ABG for hearing loss having a conductive component (Johnson and Dillon, 2011). Again, 100% restoration of the ABG may be suitable when MPO of the hearing aid can support the prescribed insertion gain for moderate to high input levels without causing the real ear aided response to saturate and degrading sound quality (Walker, 1999;Dillon, 2001;Mueller and Hornsby, 2002). ...
... 1. Advancements in hearing aid receiver technology that now offers MPO limitations of 1401 dB 2. The expected audibility improvements for soft speech by increasing gain for individuals with more conductive hearing loss than sensorineural loss 3. The modest population of hearing impaired patients who receive hearing aids each year with a diagnosis of either conductive or mixed hearing loss (z5% in the U.S. Department of Veterans Affairs health-care system) 4. The lack of consensus between current peer-reviewed and validated generic prescriptions for hearing losses with a conductive component (Johnson and Dillon, 2011) Of particular interest is whether 75% restoration of the ABG or a larger percentage is most appropriate for patients as a function of MPO limitations in hearing aids. ...
Hearing aid prescriptive recommendations for hearing losses having a conductive component have received less clinical and research interest than for losses of a sensorineural nature; as a result, much variation remains among current prescriptive methods in their recommendations for conductive and mixed hearing losses (Johnson and Dillon, 2011).
The primary intent of this brief clinical note is to demonstrate differences between two algebraically equivalent expressions of hearing loss, which have been approaches used historically to generate a prescription for hearing losses with a conductive component. When air and bone conduction thresholds are entered into hearing aid prescriptions designed for nonlinear hearing aids, it was hypothesized that that two expressions would not yield equivalent amounts of prescribed insertion gain and output. These differences are examined for their impact on the maximum power output (MPO) requirements of the hearing aid. Subsequently, the MPO capabilities of two common behind-the-ear (BTE) receiver placement alternatives, receiver-in-aid (RIA) and receiver-in-canal (RIC), are examined.
The two expressions of hearing losses examined were the 25% ABG + AC approach and the 75% ABG + BC approach, where ABG refers to air-bone gap, AC refers to air-conduction threshold, and BC refers to bone-conduction threshold. Example hearing loss cases with a conductive component are sampled for calculations. The MPO capabilities of the BTE receiver placements in commercially-available products were obtained from hearing aids on the U.S. federal purchasing contract.
Prescribed gain and the required MPO differs markedly between the two approaches. The 75% ABG + BC approach prescribes a compression ratio that is reflective of the amount of sensorineural hearing loss. Not all hearing aids will have the MPO capabilities to support the output requirements for fitting hearing losses with a large conductive component particularly when combined with significant sensorineural hearing loss. Generally, current RIA BTE products have greater output capabilities than RIC BTE products.
The 75% ABG + BC approach is more appropriate than the 25% ABG + AC approach because the latter approach inappropriately uses AC thresholds as the basis for determining the compression ratio. That is, for hearing losses with a conductive component, the AC thresholds are not a measure of sensorineural hearing loss and cannot serve as the basis for determining the amount of desired compression. The Australian National Acoustic Laboratories has been using the 75% ABG + BC approach in lieu of the 25% ABG + AC approach since its release of the National Acoustic Laboratories—Non-linear 1 (NAL-NL1) prescriptive method in 1999. Future research may examine whether individuals with conductive hearing loss benefit or prefer more than 75% restoration of the conductive component provided adequate MPO capabilities to support such restoration.
... Each procedure provides gain targets separately for adult-aged and child-aged populations. A comparison of the adult versions of the DSL m[i/o] and NAL-NL2 for five hypothetical audiograms was reported by Johnson and Dillon (2011). They found that NAL-NL2 and DSL m[i/o] provided equivalent calculated loudness and predicted speech intelligibility at medium input levels, despite variations in gain-frequency response shapes prescribed by the two procedures (Johnson & Dillon, 2011). ...
... A comparison of the adult versions of the DSL m[i/o] and NAL-NL2 for five hypothetical audiograms was reported by Johnson and Dillon (2011). They found that NAL-NL2 and DSL m[i/o] provided equivalent calculated loudness and predicted speech intelligibility at medium input levels, despite variations in gain-frequency response shapes prescribed by the two procedures (Johnson & Dillon, 2011). These findings cannot be generalized to the child-aged versions, however, because prescriptive gain targets for children differ from those for adults with the same audiogram. ...
... In contrast to these findings on children showing minimal differences in SII but vastly different loudness, the comparison of the adult versions (Johnson & Dillon, 2011) indicated that the two prescriptions were equivalent in SII and loudness. As the two prescriptions inherently prescribed less gain for adults than for children, it would not be surprising that conclusions about loudness for the two populations differ. ...
Abstract Objective: To examine the impact of prescription on predicted speech intelligibility and loudness for children. Design: A between-group comparison of speech intelligibility index (SII) and loudness, based on hearing aids fitted according to NAL-NL1, DSL v4.1, or DSL m[i/o] prescriptions. A within-group comparison of gains prescribed by DSL m[i/o] and NAL-NL2 for children in terms of SII and loudness. Study sample: Participants were 200 children, who were randomly assigned to first hearing-aid fitting with either NAL-NL1, DSL v4.1, or DSL m[i/o]. Audiometric data and hearing-aid data at 3 years of age were used. Results: On average, SII calculated on the basis of hearing-aid gains were higher for DSL than for NAL-NL1 at low input level, equivalent at medium input level, and higher for NAL-NL1 than DSL at high input level. Greater loudness was associated with DSL than with NAL-NL1, across a range of input levels. Comparing NAL-NL2 and DSL m[i/o] target gains revealed higher SII for the latter at low input level. SII was higher for NAL-NL2 than for DSL m[i/o] at medium- and high-input levels despite greater loudness for gains prescribed by DSL m[i/o] than by NAL-NL2. Conclusion: The choice of prescription has minimal effects on speech intelligibility predictions but marked effects on loudness predictions.
... Although overall ratings on auditory functional performance in real life were significantly higher for the DSL v5 prescription than for the NAL-NL1 prescription, there were increased reports from children about loudness discomfort when they used the DSL v5 prescription than when they used NAL-NL1 in real-world environments. In the present study, we adopted the modeling approach reported in a previous comparison of gain from generic hearing aid prescriptive methods (Johnson and Dillon, 2011). Two theoretical models were used. ...
... If speech intelligibility is estimated using the SII without allowing for this hearing loss desensitization, intelligibility is overpredicted whenever hearing thresholds at any frequency are severe or profound. Therefore, we evaluated the impact of prescriptions by estimating predicted speech intelligibility using not only the standard SII model, but also a modified SII model that allowed for hearing loss desensitization to provide a realistic estimate of weighted audibility when hearing aids were fit according to each prescription Johnson and Dillon, 2011).The detailed calculations will be described in the Methods section. ...
An important goal of providing amplification to children with hearing loss is to ensure that hearing aids are adjusted to match targets of prescriptive procedures as closely as possible. The Desired Sensation Level (DSL) v5 and the National Acoustic Laboratories' prescription for nonlinear hearing aids, version 1 (NAL-NL1) procedures are widely used in fitting hearing aids to children. Little is known about hearing aid fitting outcomes for children with severe or profound hearing loss.
The purpose of this study was to investigate the prescribed and measured gain of hearing aids fit according to the NAL-NL1 and the DSL v5 procedure for children with moderately severe to profound hearing loss; and to examine the impact of choice of prescription on predicted speech intelligibility and loudness.
Participants were fit with Phonak Naida V SP hearing aids according to the NAL-NL1 and DSL v5 procedures. The Speech Intelligibility Index (SII) and estimated loudness were calculated using published models.
The sample consisted of 16 children (30 ears) aged between 7 and 17 yr old.
The measured hearing aid gains were compared with the prescribed gains at 50 (low), 65 (medium), and 80 dB SPL (high) input levels. The goodness of fit-to-targets was quantified by calculating the average root-mean-square (RMS) error of the measured gain compared with prescriptive gain targets for 0.5, 1, 2, and 4 kHz. The significance of difference between prescriptions for hearing aid gains, SII, and loudness was examined by performing analyses of variance. Correlation analyses were used to examine the relationship between measures.
The DSL v5 prescribed significantly higher overall gain than the NAL-NL1 procedure for the same audiograms. For low and medium input levels, the hearing aids of all children fit with NAL-NL1 were within 5 dB RMS of prescribed targets, but 33% (10 ears) deviated from the DSL v5 targets by more than 5 dB RMS on average. For high input level, the hearing aid fittings of 60% and 43% of ears deviated by more than 5 dB RMS from targets of NAL-NL1 and DSL v5, respectively. Greater deviations from targets were associated with more severe hearing loss. On average, the SII was higher for DSL v5 than for NAL-NL1 at low input level. No significant difference in SII was found between prescriptions at medium or high input level, despite greater loudness for DSL v5 than for NAL-NL1. Conclusions: Although targets between 0.25 and 2 kHz were well matched for both prescriptions in commercial hearing aids, gain targets at 4 kHz were matched for NAL-NL1 only. Although the two prescriptions differ markedly in estimated loudness, they resulted in comparable predicted speech intelligibility for medium and high input levels.
American Academy of Audiology.
... In running speech, the peaks and valleys of speech levels vary over time, by talker, and by speech material. The peak sensation levels, all referenced as a function of frequency, are part of the variable known within NAL-NL2 as the temporary variable (K9) used in the calculation of the band audibility function (A) (Keidser et al, 2011;Ching et al, 2011;Johnson and Dillon, 2011). The K9 variable is multiplied by the A variable to yield the desensitizedband SII value. ...
... Hearing loss thresholds (dB HLs) in the better ear and hearing aid output (the real-ear aided response or REAR) were used from each participant to create accounts of modeled SII and loudness. Predicted SII was calculated across each EC using SII calculations with a revised desensitization factor described quantitatively in Johnson and Dillon (2011). Development of the factor was supported by ongoing research efforts at NAL over the past decade by several lead investigators. ...
To evaluate sound quality preferences of participants wearing hearing aids with different strengths of nonlinear frequency compression (NFC) processing versus no NFC processing. Two analysis methods, one without and one with a qualifier as to the magnitude of preferences, were compared for their percent agreement to differentiate a small difference in perceived sound quality as a result of applied NFC processing.
A single-blind design was used with participants unaware of the presence or strength of NFC processing (independent variable). The National Acoustic Laboratories-Nonlinear 2 (NAL-NL2) prescription of amplification was chosen because audibility is intentionally not prescribed in the presence of larger sensorineural hearing loss thresholds. A lack of prescribed audibility, when present, was deemed an objective qualifier for NFC. NFC is known to improve the input bandwidth available to listeners when high-frequency audibility is not otherwise available and increasing strengths of NFC were examined. Experimental condition 3 (EC3) was stronger than the manufacturer default (EC2). More aggressive strengths (e.g., EC4 and EC5), however, were expected to include excessive distortion and even reduce the output bandwidth that had been prescribed as audible by NAL-NL2 (EC1).
A total of 14 male Veterans with severe high-frequency sensorineural hearing loss.
Participant sound quality preference ratings (dependent variable) without a qualifier as to the magnitude of preference were analyzed based on binomial probability theory, as is traditional with paired comparison data. The ratings with a qualifier as to the magnitude of preference were analyzed based on the nonparametric statistic of the Wilcoxon signed rank test.
The binomial probability analysis method identified a sound quality preference as well as the nonparametric probability test method. As the strength of NFC increased, more participants preferred the EC with less NFC. Fourteen of 14 participants showed equal preference between EC1 and EC2 perhaps, in part, because EC2 showed no objective improvement in audibility for six of the 14 participants (42%). Thirteen of the 14 participants showed no preference between NAL-NL2 and EC3, but all participants had an objective improvement in audibility. With more NFC than EC3, more and more participants preferred the other EC with less NFC in the paired comparison.
By referencing the recommended sensation levels of amplitude compression (e.g., NAL-NL2) in the ear canal of hearing aid wearers, the targeting of NFC parameters can likely be optimized with respect to improvements in effective audibility that may contribute to speech recognition without adversely impacting sound quality. After targeting of NFC parameters, providers can facilitate decisions about the use of NFC parameters (strengths of processing) via sound quality preference judgments using paired comparisons.
American Academy of Audiology.
... Recently revised independent fitting procedures, National Acoustics Laboratories-Nonlinear 2 (NAL-NL2)  and desired sensation level multistage input/ output [DSL m(i/o)] , both increase sound audibility and speech intelligibility . NAL-NL2 maximizes speech intelligibility and equalizes the loudness to that perceived by normal hearer. ...
... Unlike questionnaires, the aided sound field thresholds showed no statistically significant differences between the two formulae. This is in agreement with Johnson and Dillon , who examined the impact of both formulae on seven hypothetical hearing loss configurations. They concluded that both formulae have comparable overall loudness, comparable speech intelligibility in quiet and in noise and the insertion gain differences were small for flat sensorineural hearing loss, ±5 dB. ...
... In this paper, a new nonlinear strategy, designated as 206 CHENFIT-AMP, which combines the fitting and amplification 207 procedures in a real-time signal processing scheme based on 208 Chen's loudness model, is derived and evaluated. CHENFIT-209 AMP tries to compensate for OHC loss and IHC loss separately tion of NAL-NL1 ,  or NAL-NL2 ,  only con- An online gain control strategy for hearing aids proposed by 240 Launer and Moore , which tried to compensate for OHC 241 loss and IHC loss separately, seems to have a similar idea as For an input intensity spectrum X(f ), the model first filters 257 it with the outer and middle ear transfer function OME(f ): ...
... In the derivation procedure of NAL-NL1, the previous 773 Moore's loudness model  was used and the values of OHC 774 loss and IHC loss were, respectively, fixed as 80% and 20% of 775 the value of the absolute threshold at each center frequency; in 776 the derivation procedure of NAL-NL2, the new Moore's loud-777 ness model was used  and the values of OHC loss and IHC 778 loss were, respectively, fixed as 90% and 10% of the value of 779 the absolute threshold . The basic relationship of OHC loss, 780 IHC loss, and absolute threshold in previous derivations is that 781 the dB value of absolute threshold equals to the sum of the 782 dB values of OHC loss and IHC loss. ...
CHENFIT-AMP is a novel nonlinear strategy that combines the fitting (gain prescription) and amplification (gain implementation) procedures for cochlear hearing loss. The fitting part of CHENFIT-AMP prescribes gain for outer hair cell (OHC) and inner hair cell (IHC) loss respectively. The gain for OHC loss varies with the cochlear gain decided by the value of OHC loss and the input level. The gain for IHC loss varies with the value of IHC loss only and will be limited to a constant if there is a 'dead region'. The amplification part of CHENFIT-AMP is responsible for estimating the input level and cochlear gain based on Chen's loudness model. CHENFIT-AMP is evaluated with four typical audiograms and nine individual audiograms. A widely used nonlinear fitting procedure, NAL-NL2, is evaluated to compare prescription results with CHENFIT-AMP; a standard nonlinear amplification algorithm, multi-channel compression (MCC), with the parameters provided by NAL-NL2, is also evaluated to compare amplification results with CHENFIT-AMP. For long-term average speech spectrum (LTASS) inputs, CHENFIT-AMP generally prescribes similar gain as NAL-NL2 for the typical audiograms; however, gain prescribed by CHENFIT-AMP is more individualized than NAL-NL2 for the individual audiograms, especially when the audiograms have big deviations in the slope. For LTASS-shaped noise input, the gain implemented by MCC with parameters provided by NAL-NL2 cannot completely realize the gain prescribed by NAL-NL2. For speech sentence inputs, average ratings by subjects indicated that amplification by CHENFIT-AMP was preferred and led to a louder perception than that by MCC with parameters from NAL-NL2.
... NAL-NL2 recommends gains for frequencies up to 8 kHz, whereas NAL-NL1 is limited to 6 kHz (Moore & Sek, 2013). NAL-NL2 prescribes more low-and high-frequency gain and less mid-frequency gain than NAL-NL1 (Johnson & Dillon, 2011). In addition, the gender and hearing-aid experience of the patient can be taken into account for the gain precalculation with NAL-NL2. ...
... In addition, the gender and hearing-aid experience of the patient can be taken into account for the gain precalculation with NAL-NL2. Johnson and Dillon (2011) compared the latest prescription rules CAM2, NAL-NL2, and DSL v5 Adult with regard to insertion gain, loudness, and CR. For speech at a level of 65 dB sound pressure level (SPL), DSL v5 Adult provides most gain in the high frequencies. ...
Dynamic range compression serves different purposes in the music and hearing-aid industries. In the music industry, it is used to make music louder and more attractive to normal-hearing listeners. In the hearing-aid industry, it is used to map the variable dynamic range of acoustic signals to the reduced dynamic range of hearing-impaired listeners. Hence, hearing-aided listeners will typically receive a dual dose of compression when listening to recorded music. The present study involved an acoustic analysis of dynamic range across a cross section of recorded music as well as a perceptual study comparing the efficacy of different compression schemes. The acoustic analysis revealed that the dynamic range of samples from popular genres, such as rock or rap, was generally smaller than the dynamic range of samples from classical genres, such as opera and orchestra. By comparison, the dynamic range of speech, based on recordings of monologues in quiet, was larger than the dynamic range of all music genres tested. The perceptual study compared the effect of the prescription rule NAL-NL2 with a semicompressive and a linear scheme. Music subjected to linear processing had the highest ratings for dynamics and quality, followed by the semicompressive and the NAL-NL2 setting. These findings advise against NAL-NL2 as a prescription rule for recorded music and recommend linear settings.
... One chief barrier to the wider use of amplification has been that hearing aids often make speech louder without improving clarity, especially in background noise (Johnson and Dillon, 2011). This phenomenon may arise from the effects of hearing loss on central processing of speech. ...
... Perceptual studies also suggest exaggerated encoding of the envelope in humans with unilateral hearing loss (Moore et al., 1996) and potentially reduced ability to use TFS cues (Lorenzi et al., 2006). These effects might explain the hearing impaired listener's complaint that speech is loud yet unclear (Johnson and Dillon, 2011). ...
Aging results in a loss of sensory function, and the effects of hearing impairment can be especially devastating due to reduced communication ability. Older adults with hearing loss report that speech, especially in noisy backgrounds, is uncomfortably loud yet unclear. Hearing loss results in an unbalanced neural representation of speech: the slowly-varying envelope is enhanced, dominating representation in the auditory pathway and perceptual salience at the cost of the rapidly-varying fine structure. We hypothesized that older adults with hearing loss can be trained to compensate for these changes in central auditory processing through directed attention to behaviorally-relevant speech sounds. To that end, we evaluated the effects of auditory-cognitive training in older adults (ages 55-79) with normal hearing and hearing loss. After training, the auditory training group with hearing loss experienced a reduction in the neural representation of the speech envelope presented in noise, approaching levels observed in normal hearing older adults. No changes were noted in the control group. Importantly, changes in speech processing were accompanied by improvements in speech perception. Thus, central processing deficits associated with hearing loss may be partially remediated with training, resulting in real-life benefits for everyday communication.
... Hearing aids (HAs) are the main intervention for people with hearing loss and have undergone significant advances in digital technology over the last two decades. Whilst satisfaction with HAs has improved since the 1990s (Kochkin, 2010), users often continue to encounter difficulties in challenging listening conditions (Johnson and Dillon, 2011). Early studies with HA users showed an association between behavioral and subjective HA outcomes and measures of cognitive skills Lunner, 2003). ...
Auditory training (AT) helps compensate for degradation in the auditory signal. A series of three high-quality training studies are discussed, which include, (i) a randomized controlled trial (RCT) of phoneme discrimination in quiet that trained adults with mild hearing loss (n = 44), (ii) a repeated measures study that trained phoneme discrimination in noise in hearing aid (HA) users (n = 30), and (iii) a double-blind RCT that directly trained working memory (WM) in HA users (n = 57). AT resulted in generalized improvements in measures of self-reported hearing, competing speech, and complex cognitive tasks that all index executive functions. This suggests that for AT related benefits, the development of complex cognitive skills may be more important than the refinement of sensory processing. Furthermore, outcome measures should be sensitive to the functional benefits of AT. For WM training, lack of far-transfer to untrained outcomes suggests no generalized benefits to real-world listening abilities. We propose that combined auditory-cognitive training approaches, where cognitive enhancement is embedded within auditory tasks, are most likely to offer generalized benefits to the real-world listening abilities of adults with hearing loss.
... Enter desensitization as an additional factor to the existing SII model. Desensitization has been reported to not be frequency-specific and is consistent with the results and interpretation of findings from Hornsby and Ricketts (2003) and Hornsby and colleagues (2011) (Ching et al., 2011; Johnson & Dillon, 2011; Ching & Dillon, 2013). Rather, desensitization is specific to the magnitude of hearing loss. ...
... En comparaison de ces écarts entre les fabricants pour une même méthode générique et un même audiogramme, il importe de relater les écarts relevés par Johnson & al (2011) par comparaison théorique des écarts introduits par les créateurs de méthodes euxmêmes . (Figure 4). ...
... The amount of intelligible speech information that can be extracted from an audible signal decreases as hearing loss increases (Carhart, 1951;Ching, Dillon, & Byrne, 1998;Hogan & Turner, 1998;Pavlovic, Studebaker, & Sherbecoe, 1986;Studebaker, Sherbecoe, McDaniel, & Gray, 1997). This decreased ability of the impaired ear is commonly referred to as hearing loss desensitization (HLD) and has recently been demonstrated as not frequency specific (Ching, Dillon, Lockhart, van Wanrooy, & Flax, 2011;Johnson & Dillon, 2011), consistent with the results and Johnson 3 ...
A major decision at the time of hearing aid fitting and dispensing is the amount of amplification to provide listeners (both adult and pediatric populations) for the appropriate compensation of sensorineural hearing impairment across a range of frequencies (e.g., 160-10000 Hz) and input levels (e.g., 50-75 dB sound pressure level). This article describes modern prescription theory for hearing aids within the context of a risk versus return trade-off and efficient frontier analyses. The expected return of amplification recommendations (i.e., generic prescriptions such as National Acoustic Laboratories-Non-Linear 2, NAL-NL2, and Desired Sensation Level Multiple Input/Output, DSL m[i/o]) for the Speech Intelligibility Index (SII) and high-frequency audibility were traded against a potential risk (i.e., loudness). The modeled performance of each prescription was compared one with another and with the efficient frontier of normal hearing sensitivity (i.e., a reference point for the most return with the least risk). For the pediatric population, NAL-NL2 was more efficient for SII, while DSL m[i/o] was more efficient for high-frequency audibility. For the adult population, NAL-NL2 was more efficient for SII, while the two prescriptions were similar with regard to high-frequency audibility. In terms of absolute return (i.e., not considering the risk of loudness), however, DSL m[i/o] prescribed more outright high-frequency audibility than NAL-NL2 for either aged population, particularly, as hearing loss increased. Given the principles and demonstrated accuracy of desensitization (reduced utility of audibility with increasing hearing loss) observed at the group level, additional high-frequency audibility beyond that of NAL-NL2 is not expected to make further contributions to speech intelligibility (recognition) for the average listener.
... The results of these studies showed that prescriptive gain and general loudness of DSLm [i/o] method was higher than for NAL-Nl2 in all frequencies ranges. This difference was significant at low frequencies, while it reduces at middle frequencies [23,24]. According to study conducted by Dillon (2012) similar results were obtained for flat audiograms and he concluded that DSLm [i/o] procedure prescribe more gain than NAL-NL2 for loudness normalization while less amplification is prescribed with NAL-NL2 method because low frequencies do not have a key role in speech intelligibility . ...
... Typically, hearing aid prescriptive procedures have the goal of providing audibility over as wide a frequency range as possible. But prescriptive procedures differ in recommendations of insertion gain as a function of frequency and also differ with regard to the recommended hearing aid bandwidth (Johnson & Dillon, 2011). The ability to make sound audible through the hearing aid at high frequencies (at and above 3000 Hz) will be governed by the degree of hearing loss. ...
The purpose of this study was to determine how the bandwidth of the hearing aid (HA) fitting affects bimodal speech recognition of listeners with a cochlear implant (CI) in one ear and severe-to-profound hearing loss in the unimplanted ear (but with residual hearing sufficient for wideband amplification using National Acoustic Laboratories Revised, Profound [NAL-RP] prescriptive guidelines; unaided thresholds no poorer than 95 dB HL through 2000 Hz).
Recognition of sentence material in quiet and in noise was measured with the CI alone and with CI plus HA as the amplification provided by the HA in the high and mid-frequency regions was systematically reduced from the wideband condition (NAL-RP prescription). Modified bandwidths included upper frequency cutoffs of 2000, 1000, or 500 Hz.
On average, significant bimodal benefit was obtained when the HA provided amplification at all frequencies with aidable residual hearing. Limiting the HA bandwidth to only low-frequency amplification (below 1000 Hz) did not yield significant improvements in performance over listening with the CI alone.
These data suggest the importance of providing amplification across as wide a frequency region as permitted by audiometric thresholds in the HA used by bimodal users.
... This is, however, in agreement with the general principle that prescription procedures provide a baseline response that is assumed to be appropriate for the average listener and from which fine-tuning to individual preferences can be made. A comparison of NAL-NL2 with other generic prescription procedures, including NAL-NL1, in terms of impact on loudness and speech intelligibility is presented by Johnson and Dillon (2011). This investigation confirms, that relative to NAL-NL1, lower overall loudness that is also well below normal overall loudness is achieved with NAL-NL2. ...
NAL-NL1, the first procedure from the National Acoustic Laboratories (NAL) for prescribing nonlinear gain, was a purely theoretically derived formula aimed at maximizing speech intelligibility for any input level of speech while keeping the overall loudness of speech at or below normal loudness. The formula was obtained through an optimization process in which speech intelligibility and loudness were predicted from selected models. Using updated models and applying some revisions to the derivation process, a theoretically derived NAL-NL2 formula was obtained in a similar way. Further adjustments, directed by empirical data collected in studies using NAL-NL1 as the baseline response, have been made to the theoretically derived formula. Specifically, empirical data have demonstrated that (a) female hearing aid users prefer lower overall gain than male users; (b) new hearing aid users with more than a mild hearing loss prefer increasingly less gain with increasing degree of hearing loss than experienced hearing aid users, and require up to 2 years to adapt to gain levels selected by experienced hearing aid users; (c) unilaterally and bilaterally fitted hearing aid users prefer overall gain levels that vary less than estimated by the bilateral correction factor; (d) adults prefer lower overall gain than children; and (e) people with severe/profound hearing loss prefer lower compression ratios than predicted when fitted with fast-acting compression. The literature and data leading to these conclusions are summarized and discussed in this article, and the procedure for implementing the adjustments to the theoretically derived NAL-NL2 formula is described.
... As mentioned earlier, two new fitting methods have been introduced, the NAL-NL2 method (Keidser et al., 2011) and the CAM2 method (Moore, Glasberg et al., 2010). NAL-NL2 recommends less mid-frequency gain and more low-and high-frequency gain than NAL-NL1 (Johnson & Dillon, 2011). NAL-NL2 recommends gain for frequencies up to 8 kHz, whereas the limit for NAL-NL1 is 6 kHz. ...
This article reviews a series of studies on the factors influencing sound quality preferences, mostly for jazz and classical music stimuli. The data were obtained using ratings of individual stimuli or using the method of paired comparisons. For normal-hearing participants, the highest ratings of sound quality were obtained when the reproduction bandwidth was wide (55 to 16000 Hz) and ripples in the frequency response were small (less than ± 5 dB). For hearing-impaired participants listening via a simulated five-channel compression hearing aid with gains set using the CAM2 fitting method, preferences for upper cutoff frequency varied across participants: Some preferred a 7.5- or 10-kHz upper cutoff frequency over a 5-kHz cutoff frequency, and some showed the opposite preference. Preferences for a higher upper cutoff frequency were associated with a shallow high-frequency slope of the audiogram. A subsequent study comparing the CAM2 and NAL-NL2 fitting methods, with gains slightly reduced for participants who were not experienced hearing aid users, showed a consistent preference for CAM2. Since the two methods differ mainly in the gain applied for frequencies above 4 kHz (CAM2 recommending higher gain than NAL-NL2), these results suggest that extending the upper cutoff frequency is beneficial. A system for reducing "overshoot" effects produced by compression gave small but significant benefits for sound quality of a percussion instrument (xylophone). For a high-input level (80 dB SPL), slow compression was preferred over fast compression.
... The NAL procedure aims to maximize predicted speech intelligibility while limiting total loudness to no greater than that perceived by a normal hearer listening to the same sound; whereas the DSL procedure aims to normalize loudness at different frequencies. For this reason, the prescriptions sometimes differ markedly in terms of gainfrequency responses for the same audiometric confi gurations (Byrne et al, 2001;Johnson & Dillon, 2011). Despite their worldwide adoption, the relative effectiveness of the respective prescriptions for supporting children ' s speech and language development is yet to be established. ...
To determine the influence of choice of prescription and other child-, family- and intervention-related factors on speech, language, and functional performance of hearing-impaired children by three years of age.
Design and study sample:
A randomized controlled design was implemented as part of a population-based, longitudinal study on outcomes of children with hearing impairment (LOCHI) in Australia. Two hundred and eighteen children were randomly assigned to either the NAL or the DSL prescription for first fitting of hearing aids. Their performance outcomes were evaluated.
Prescriptive targets were closely matched in children's hearing aids. There were no significant differences in children's language, speech production, or functional performance between prescriptions. Parents' ratings of children's device usage and loudness discomfort were not significantly different between prescription groups. Functional performance within the first year of fitting together with degree of hearing loss, presence of additional disabilities, and maternal education explained 44% of variation in language ability of children by three years of age.
There was no significant association between choice of hearing-aid prescription and variance in children's outcomes at three years of age. In contrast, additional disability, maternal educational level, and early functional performance were significant predictive factors of children's outcomes.
... 20 Despite recent advances in digital technology and improved users' satisfaction with hearing aids, 21 users often continue to encounter difficulties in noisy and challenging listening environments. 22,23 Furthermore, a large proportion of people who would benefit from hearing aids do not have them, 24 and those who do wear hearing aids often delay seeking help, with many people having hearing difficulties for at least 10 years before obtaining hearing aids. 1 When it comes to improving communication for people with hearing loss, it is clear that hearing aids alone are not the only option. A holistic approach to aural rehabilitation has been suggested, 25 which includes management strategies to improve sensory deficits such as hearing aids and FM or wireless systems, instruction on technology and communication strategies, counseling to enhance participation in everyday life, and perceptual training. ...
Auditory training aims to compensate for degradation in the auditory signal and is offered as an intervention to help alleviate the most common complaint in people with hearing loss, understanding speech in a background noise. Yet there remain many unanswered questions. This article reviews some of the key pieces of evidence that assess the evidence for whether, and how, auditory training benefits adults with hearing loss. The evidence supports that improvements occur on the trained task; however, transfer of that learning to
generalized real-world benefit is much less robust. For more than a decade, there has been an increasing awareness of the role that cognition plays in listening. But more recently in the auditory training literature,
there has been an increased focus on assessing how cognitive performance relevant for listening may improve with training. We argue that this is specifically the case for measures that index executive processes,
such as monitoring, attention switching, and updating of working memory, all of which are required for successful listening and communication in challenging or adverse listening conditions. We propose
combined auditory-cognitive training approaches, where training interventions develop cognition embedded within auditory tasks, which are most likely to offer generalized benefits to the real-world listening abilities of people with hearing loss.
... The DSL v5.0-adult target uses a prescribed compression threshold and includes output limiting but not all targets aim for audibility. However, the DSL target does prescribe 0-20 dB more high frequency gain than NAL-NL2, depending on hearing loss configuration (Johnson and Dillon 2011). As such, using the DSL target may provide a stringent assessment of the clinically usable bandwidth of hearing aids. ...
Objective: In contrast to the past, some current hearing aids can provide gain for frequencies above 4–5 kHz. This study assessed the effect of wider bandwidth on outcome measures using hearing aids fitted with the DSL v5.0 prescription.
Design: There were two conditions: an extended bandwidth condition, for which the maximum available bandwidth was provided, and a restricted bandwidth condition, in which gain was reduced for frequencies above 4.5 kHz. Outcome measures were assessed in both conditions.
Study sample: Twenty-four participants with mild-to-moderately-severe sensorineural high-frequency sloping hearing loss.
Results: Providing extended bandwidth resulted in maximum audible output frequency values of 7.5 kHz on average for an input level of 65 dB SPL. An improvement in consonant discrimination scores (4.1%), attributable to better perception of /s/, /z/, and /t/ phonemes, was found in the extended bandwidth condition, but no significant change in loudness perception or preferred listening levels was found. Most listeners (79%) had either no preference (33%) or some preference for the extended bandwidth condition (46%).
Conclusions: The results suggest that providing the maximum bandwidth available with modern hearing aids fitted with DSL v5.0, using targets from 0.25 to 8 kHz, can be beneficial for the tested population.
... The Able Planet PS2500AMP (Able Planet) in-ear amplifier has 8 channels with 12 gain adjustment bands, noise reduction, feedback cancellation, and directionality. The participants selected their preferred amplification mode among 4 presets after listening to the Korean standard sentence lists for adults (KS-SL-A) of the Korean Standard Audiometry (KSA) test  in a quiet environment. The PSAP contains a 'natural directionality' feature as the default, and its settings could not be modified. ...
Background and objectives:
This study aimed to compare functional hearing with the use of a personal sound amplification product (PSAP) or a basic hearing aid (HA) among sensorineural hearing impaired listeners.
Subjects and methods:
Nineteen participants with mild-to-moderate sensorineural hearing loss (SNHL) (26-55 dB HL; pure-tone average, 0.5-4 kHz) were prospectively included. No participants had prior experience with HAs or PSAPs. Audiograms, speech intelligibility in both quiet and noisy environments, speech quality, and preference were assessed in three different listening conditions: unaided, with the HA, and with the PSAP.
The use of PSAP was associated with significant improvement in pure-tone thresholds at 1, 2, and 4 kHz compared to the unaided condition (all p <0.01). In the quiet environment, speech intelligibility was significantly improved after wearing a PSAP compared to the unaided condition (p <0.001), and this improvement was better than the result obtained with the HA. The PSAP also demonstrated similar improvement in the most comfortable levels compared to those obtained with the HA (p <0.05). However, there was no significant improvement of speech intelligibility in a noisy environment when wearing the PSAP (p =0.160). There was no significant difference in the reported speech quality produced by either device or in participant preference for the PSAP or HA.
The current result suggests that PSAPs provide considerable benefits to speech intelligibility in a quiet environment and can be a good alternative to compensate for mild-to-moderate SNHL.
... Prescriptive procedures are developed progressively by different researchers in order to suggest appropriate gain values for different frequency bands of digital hearing aids . The exclusive gain calculation algorithms built in the different prescriptive procedures primarily consider the measured minimum hearing threshold during audiological investigations . ...
Of late, there has been an increase in hearing impairment cases and to provide the most advantageous solutions to them is an uphill task for audiologists. Significant difficulty faced by the audiologists is in effective programming of hearing aids to provide enhanced satisfaction to the users. The main aim of our study was to develop a software intelligent system (SIS): (i) to perform the required audiological investigations for finding the degree and type of hearing loss, and (ii) to suggest appropriate values of hearing aid parameters for enhancing the speech intelligibility and the satisfaction level among the hearing aid users. In this paper, we present a Neuro-Fuzzy based SIS to automatically predict and suggest the hearing-aid parameters such as gain values, compression ratio and threshold knee point, which are needed to be fixed for different octave frequencies of sound inputs during the hearing-aid trial. The test signals for audiological investigations are generated through the standard hardware present in a personal computer system and with the aid of a software algorithm. The proposed system was validated with 243 subjects’ data collected at the Government General Hospital, Chennai, India. The calculated sensitivity, specificity and accuracy of the proposed audiometer incorporated in the SIS were 98.6%, 96.4 and 98.2%, respectively, by comparing its interpretations with those of the ‘gold standard’ audiometers. Furthermore, 91% (221 of 243) of the hearing impaired subjects attained satisfaction in the first hearing aid trials itself with the gain values as recommended by the improved SIS. The proposed system reduced around 75% of the ‘trial and error’ time spent by audiologists for enhancing satisfactory usage of the hearing aid. Hence, the proposed SIS could be used to find the degree and type of hearing loss and to recommend hearing aid parameters to provide optimal solutions to the hearing aid users.
... The existing prescriptive procedures for hearing-aid gain suggestions do not provide increased satisfaction levels among the hearing-impaired subjects across the globe because of many factors [17,18]. Johnson et al. analysed the impact of prescriptive procedures in the aspects of loudness, frequency, bandwidth, and speech intelligibility . Keidser et al. insisted on the need for self-assessment for the level of satisfaction while using a hearingaid . ...
... The aim of DSL v5.0 is to ensure loudness comfort and audibility of a wide frequency range across multiple input levels (Scollie et al., 2005). Depending on the degree, configuration, and type of hearing loss as well as input level, these two approaches may lead to very similar targets (within 1 dB) or very different targets (15 dB or more difference between prescriptive methods) (Johnson & Dillon, 2011). ...
The value of using real-ear measures when fitting hearing aids has been well researched and the information is readily available in the literature. However, a review of recent research showed that there is limited evidence to determine whether real-ear targets for gain and output can be achieved with current technology. Seven experienced clinicians fitted hearing aids to real-ear targets using one of two prescriptive methods: National Acoustic Laboratories, Non-Linear, version 1 (NAL-NL1) and Desired Sensation Level, version 5 (DSL v5.0, adult targets). One hundred ears were assessed for DSL v5.0 and 134 ears were assessed for NAL-NL1 to determine how closely the fittings matched real ear targets. The results indicate that a hearing aid can be matched to target within ±5 dB regardless of the number of gain adjustment handles, the manufacturer, or the style; with the exception of severe/profound hearing loss, particularly in the high frequencies.
... The reason was not for preventing PTS but rather reasoned theory of amplification acceptance based on loudness preference data from listeners with hearing impairment. The reduction in gain for adults occurs by constraining loudness to less than that of the person with normal hearing sensitivity (Johnson & Dillon, 2011). ...
Objective: To determine safe output sound pressure levels (SPL) for sound amplification devices to preserve hearing sensitivity after usage.
Design: A mathematical model consisting of the Modified Power Law (MPL) (Humes & Jesteadt, 1991 Humes, L.E. & Jesteadt, W. 1991. Modeling the interactions between noise exposure and other variables. J Acoust Soc Am, 90, 182–188.[CrossRef], [PubMed], [Web of Science ®] [Google Scholar]) combined with equations for predicting temporary threshold shift (TTS) and subsequent permanent threshold shift (PTS) (Macrae, 1994b Macrae, J.H. 1994b. Prediction of asymptotic threshold shift caused by hearing aid use. J Speech Hear Res, 37, 1450–1458.[CrossRef], [PubMed] [Google Scholar]) was used to determine safe output SPL. Study sample: The study involves no new human subject measurements of loudness tolerance or threshold shifts. PTS was determined by the MPL model for 234 audiograms and the SPL output recommended by four different validated prescription recommendations for hearing aids. Results: PTS can, on rare occasion, occur as a result of SPL delivered by hearing aids at modern day prescription recommendations. The trading relationship of safe output SPL, decibel hearing level (dB HL) threshold, and PTS was captured with algebraic expressions. Better hearing thresholds lowered the safe output SPL and higher thresholds raised the safe output SPL. Conclusion: Safe output SPL can consider the magnitude of unaided hearing loss. For devices not set to prescriptive levels, limiting the output SPL below the safe levels identified should protect against threshold worsening as a result of long-term usage.
... However, we noted during study implementation that fitting ranges typically do not change when the fitting formula is changed, despite differences in gain requirements across prescriptions. We also note that between-target differences increase as the hearing loss becomes more severe (Johnson and Dillon, 2011;Ching et al, 2015). It is, therefore, possible that some recommended fitting ranges were not specific to DSL targets, and that this may have impacted whether the fitted devices in fact had enough power to provide a good match to targets. ...
Hearing aid prescriptive methods are a commonly recommended component of evidence-based preferred practice guidelines and are often implemented in the hearing aid programming software. Previous studies evaluating hearing aid manufacturers' software-derived fittings to prescriptions have shown significant deviations from targets. However, few such studies examined the accuracy of software-derived fittings for the Desired Sensation Level (DSL) v5.0 prescription.
The purpose of this study was to evaluate the accuracy of software-derived fittings to the DSL v5.0 prescription, across a range of hearing aid brands, audiograms, and test levels.
This study is a prospective chart review with simulated cases.
Data collection and analysis:
A set of software-derived fittings were created for a six-month-old test case, across audiograms ranging from mild to profound. The aided output from each fitting was verified in the test box at 55-, 65-, 75-, and 90-dB SPL, and compared with DSL v5.0 child targets. The deviations from target across frequencies 250-6000 Hz were calculated, together with the root-mean-square error (RMSE) from target. The aided Speech Intelligibility Index (SII) values generated for the speech passages at 55- and 65-dB SPL were compared with published norms.
Thirteen behind-the-ear style hearing aids from eight manufacturers were tested.
The amount of deviation per frequency was dependent on the test level and degree of hearing loss. Most software-derived fittings for mild-to-moderately severe hearing losses fell within ±5 dB of the target for most frequencies. RMSE results revealed more than 84% of those hearing aid fittings for the mild-to-moderate hearing losses were within 5 dB at all test levels. Fittings for severe to profound hearing losses had the greatest deviation from target and RMSE. Aided SII values for the mild-to-moderate audiograms fell within the normative range for DSL pediatric fittings, although they fell within the lower portion of the distribution. For more severe losses, SII values for some hearing aids fell below the normative range.
In this study, use of the software-derived manufacturers' fittings based on the DSL v5.0 pediatric targets set most hearing aids within a clinically acceptable range around the prescribed target, particularly for mild-to-moderate hearing losses. However, it is likely that clinician adjustment based on verification of hearing aid output would be required to optimize the fit to target, maximize aided SII, and ensure appropriate audibility across all degrees of hearing loss.
... However, we noted during study implementation that fitting ranges typically do not change when the fitting formula is changed, despite differences in gain requirements across prescriptions. We also note that between-target differences increase as the hearing loss becomes more severe (Johnson and Dillon, 2011;Ching et al, 2015). It is, therefore, possible that some recommended fitting ranges were not specific to DSL targets, and that this may have impacted whether the fitted devices in fact had enough power to provide a good match to targets. ...
Background: Hearing aid prescriptive methods are a commonly recommended component of evidencebasedpreferred practice guidelines and are often implemented in the hearing aid programming software.Previous studies evaluating hearing aid manufacturers’ software-derived fittings to prescriptionshave shown significant deviations from targets. However, few such studies examined the accuracy ofsoftware-derived fittings for the Desired Sensation Level (DSL) v5.0 prescription.
Purpose: The purpose of this study was to evaluate the accuracy of software-derived fittings to the DSLv5.0 prescription, across a range of hearing aid brands, audiograms, and test levels.
Research Design: This study is a prospective chart review with simulated cases.
Data Collection and Analysis: A set of software-derived fittings were created for a six-month-old testcase, across audiograms ranging from mild to profound. The aided output from each fitting was verified inthe test box at 55-, 65-, 75-, and 90-dB SPL, and compared with DSL v5.0 child targets. The deviationsfrom target across frequencies 250–6000 Hz were calculated, together with the root-mean-square error(RMSE) from target. The aided Speech Intelligibility Index (SII) values generated for the speech passagesat 55- and 65-dB SPL were compared with published norms.
Study Sample: Thirteen behind-the-ear style hearing aids from eight manufacturers were tested.
Results: The amount of deviation per frequency was dependent on the test level and degree of hearingloss. Most software-derived fittings for mild-to-moderately severe hearing losses fell within ±5 dB of thetarget for most frequencies. RMSE results revealed more than 84 percent of those hearing aid fittings for themild-to-moderate hearing losses were within 5 dB at all test levels. Fittings for severe to profound hearinglosses had the greatest deviation from target and RMSE. Aided SII values for the mild-to-moderate audiogramsfell within the normative range for DSL pediatric fittings, although they fell within the lower portionof the distribution. For more severe losses, SII values for some hearing aids fell below the normative range.
Conclusions: In this study, use of the software-derived manufacturers’ fittings based on the DSL v5.0pediatric targets set most hearing aids within a clinically acceptable range around the prescribed target,particularly for mild-to-moderate hearing losses. However, it is likely that clinician adjustment based onverification of hearing aid output would be required to optimize the fit to target, maximize aided SII, andensure appropriate audibility across all degrees of hearing loss.<br /
... One form of hearing intervention is fitting hearing aids, yet aided listeners still report difficulties in SiN listening. This suggests that hearing aid intervention alone is not beneficial enough to improving SiN listening (Johnson et al., 2011). More recent studies have suggested that a combination of auditory and cognitive training might be a beneficial route in improving SiN listening in aided listening Rudner, 2016;Tremblay et al., 2016;Yu et al., 2017). ...
This thesis investigated the role of cognition and hearing sensitivity in Speech-in-Noise (SiN) perception across different listener groups and SiN listening conditions. A typical approach to investigating the contribution of cognition is correlating cognitive ability to SiN intelligibility in populations controlled for or varied in age and/or hearing sensitivity. However, using this approach to advance our understanding of the contribution of cognition, and its potential interaction with age and hearing loss, for SiN perception has been limited by a combination of: A lack of systematicity in selection of SiN perception tests and a lack of theoretical rigor in selection of cognitive tests, a lack of comparability across studies due to differences in both cognitive test and SiN perception test selections, and in differences in age or hearing sensitivity ranges among tested populations, and the limitations of using a correlation study approach. Therefore, the main focus of the thesis will be to generate evidence to overcome these limitations in three purpose-designed investigations, discussed in chapters two, three and four respectively. In chapter two I report a systematic review and meta-analysis which took a systematic and theory driven approach to comprehensively and quantitatively assess published evidence for the role of cognition in SiN perception. The results of this chapter suggest a general association of r~.3 between cognitive performance and SiN perception, although some variability in association appeared to exist depending on cognitive domain and SiN target or masker assessed. In chapter three I present a study which used a theory-driven and systematic approach to investigate the contribution of cognition and listener characteristics (namely age and hearing sensitivity differences across younger and older listener groups) for SiN perception in different SiN conditions, using an association study design. The study revealed that the Central Executive contributed to SiN perception performance in older, but not younger listeners, regardless of SiN condition. Phonological Loop processing was important for both listener groups, but with a different role depending on age group and masker type. Episodic Buffer ability only contributed to SiN performance for older listeners, and was modulated by hearing sensitivity and background masker. In chapter four, building on the association study findings, I report a dual-task study that manipulated the availability of specific cognitive abilities for SiN perception for younger adult listeners. Here I provided further evidence to show Phonological Loop ability is more important than Central Executive ability and Episodic Buffer ability for SiN perception for this listener group, using a carefully controlled experimental design. In summary, the evidence from this thesis indicates that the role of different cognitive abilities for SiN perception can differ depending on age, hearing sensitivity and listening condition. Additionally, using a systematic approach and combining multiple methodological techniques has been informative in investigating these roles to a greater extent than has previously been achieved in the literature.
... The fitting rule considers the impact of hearing loss in a frequency band on the ability to extract speech information within this frequency band. For severeto-profound hearing losses, the fitting rule will lower the prescribed gain for frequencies that do not contribute to speech perception and will focus on more amplification on the frequencies with the better ability to extract speech cues (Johnson & Dillon, 2011;Keidser et al., 2011). English et al. (2016) conducted a study on the effect of balancing and the use of NAL-NL2 as HA prescription in bimodal CI users. ...
The aim of the study was to investigate the effect of 3 hearing aid fitting procedures on provided gain of the hearing aid in bimodal cochlear implant users and their effect on bimodal benefit.
This prospective study measured hearing aid gain and auditory performance in a cross-over design in which 3 hearing aid fitting methods were compared. Hearing aid fitting methods differed in initial gain prescription rule (NAL-NL2 and Audiogram+) and loudness balancing method (broadband vs. narrowband loudness balancing). Auditory functioning was evaluated by a speech-in-quiet test, a speech-in-noise test, and a sound localization test. Fourteen postlingually deafened adult bimodal cochlear implant users participated in the study.
No differences in provided gain and in bimodal performance were found for the different hearing aid fittings. For all hearing aid fittings, a bimodal benefit was found for speech in noise and sound localization.
Our results confirm that cochlear implant users with residual hearing in the contralateral ear substantially benefit from bimodal stimulation. However, on average, no differences were found between different types of fitting methods, varying in prescription rule and loudness balancing method.
... It considers the impact of raised hearing thresholds on the ability to extract speech information within separate frequency bands. For severe to profound hearing losses, the fitting formula will lower the prescribed gain for frequencies that are not expected to contribute to speech perception and provide more amplification for the frequencies with the better ability to extract speech cues (Johnson & Dillon 2011;Keidser et al. 2012). NAL-based fitting formulas have also been used frequently in bimodal HA fitting (Ching et al. 2001a;Perreau et al. 2013;Messersmith et al. 2015;English et al. 2016). ...
To investigate the possible advantage of the use of a dedicated bimodal hearing aid fitting formula, the Adaptive Phonak Digital Bimodal (APDB), compared with a frequently used standard hearing aid fitting formula, the NAL-NL2. We evaluated the effects of bimodal hearing aid fitting on provided hearing aid gain and on bimodal auditory functioning in a group of experienced bimodal cochlear implant (CI) users. A second aim of our study was to determine the effect of broadband loudness balancing on the prescribed gain of those two fitting formulas.
This prospective study used a crossover design in which two fitting methods were compared varying in basic prescription formula (NAL-NL2 or APDB fitting formula). The study consisted of a three-visit crossover design with 3 weeks between sessions. Nineteen postlingually deafened experienced bimodal CI users participated in this study. Auditory functioning was evaluated by a speech in quiet test, a speech in noise test, and a questionnaire on auditory performance.
Significant differences between the two fitting formulas were found for frequencies of 2000 Hz and above. For these frequencies, less gain was provided by the APDB fitting formula compared with NAL-NL2. For the APDB fitting formula, a higher compression ratio for frequencies of 1000 Hz and above was found compared with the NAL-NL2 fitting formula. Loudness balancing did not result in large deviations from the prescribed gain by the initial fitting formula. Bimodal benefit was found for speech perception in quiet and for speech perception in noise. No differences in auditory performance were found between the two fitting formulas for any of the auditory performance tests.
The results of this study show that CI users with residual hearing at the contralateral ear can benefit from bimodal stimulation, regardless of the fitting method that was applied. Although significant differences between the output and compression ratio of the NAL-NL2 and the APDB fitting formula existed, no differences in bimodal auditory performance were observed. Therefore, NAL-NL2 or the APDB fitting prescription both seem suited for bimodal fitting purposes. Additional loudness balancing has a marginal effect on the provided hearing aid output.
Objective: For a group of bimodal subjects with moderate to severe hearing loss contralateral to the cochlear implant (CI), the bimodal benefit of the hearing aid (HA) gain prescriptions DSL v5.0, NAL-NL2 and the recipients’ own gain setting were assessed.
Design: Speech perception in quiet and in noise as well as self-reported ratings of benefit were determined for all three gain-settings. Speech tests were performed in the bimodal, the HA alone and the CI alone condition. The bimodal benefit was assessed for each prescription as the difference score of the bimodal condition and the better ear.
Study Sample: Twenty adults with post-lingual hearing loss.
Results: Speech perception with DSL v5.0 was significantly higher compared to NAL-NL2 and the own prescription in both quiet and noise. The median bimodal benefit was highest for DSL v5.0 with an average of 15 percentage points for both words in quiet and sentences in noise.
Conclusions: DSL v5.0 and NAL-NL2 are both suitable for HA fitting in bimodal users. For subjects with moderate to severe hearing loss and HA experience contralateral to the implanted side, DSL v5.0 may provide better speech perception and bimodal benefit.
In this article, we explore and report the prevalence of speech in noise difficulties across multiple patient populations and reveal and speculate on management of the same. Speech in Noise problems is commonly associated with sensorineural hearing loss. The inability to understand speech in noise is often associated with, and attributed to, sensorineural hearing loss. However, some 12-15% of adults with normal hearing thresholds (i.e., pure tones) have difficulty hearing and struggle to understand speech in noise. Many of these same symptoms are present in people with neurocognitive disorders, advanced age, traumatic brain injury and more. As such, we recommend speech in noise testing on all adults who report these same difficulties. Further, once speech in noise difficulty has been objectively identified and quantified, an appropriate goal would be to improve the patient’s speech in noise ability through aural rehabilitation, as well as modern technological advances.
The objective of this experiment was to examine the contributions of audibility to the ability to perceive a gap in noise for children and adults. Sensorineural hearing loss (SNHL) in adulthood is associated with a deficit in gap detection. It is well known that reduced audibility in adult listeners with SNHL contributes to this deficit; however, it is unclear the extent to which hearing aid amplification can restore gap-detection thresholds, and the effect of childhood SNHL on gap-detection thresholds have not been described. For adults, it was hypothesized that restoring the dynamic range of hearing for listeners with SNHL would lead to approximately normal gap-detection thresholds. Children with normal hearing (NH) exhibit poorer gap-detection thresholds than adults. Because of their hearing loss, children with SNHL have less auditory experience than their peers with NH. Yet, it is unknown the extent to which auditory experience impacts their ability to perceive gaps in noise. Even with the provision of amplification, it was hypothesized that children with SNHL would show a deficit in gap detection, relative to their peers with normal hearing, because of reduced auditory experience.
The ability to detect a silent interval in noise was tested by adapting the stimulus level required for detection of gap durations between 3 and 20 ms for adults and children with and without SNHL. Stimulus-level thresholds were measured for participants with SNHL without amplification and with two prescriptive procedures-the adult and child versions of the desired sensation level i/o program-using a hearing aid simulator. The child version better restored the normal dynamic range than the adult version. Adults and children with NH were tested without amplification.
When fitted using the procedure that best restored the dynamic range, adults with SNHL had stimulus-level thresholds similar to those of adults with normal hearing. Compared to the children with NH, the children with SNHL required a higher stimulus level to detect a 5-ms gap, despite having used the procedure that better restored the normal dynamic range of hearing. Otherwise, the two groups of children had similar stimulus-level thresholds.
These findings suggest that apparent deficits in temporal resolution, as measured using stimulus-level thresholds for the detection of gaps, are dependent on age and audibility. These novel results indicate that childhood SNHL may impair temporal resolution as measured by stimulus-level thresholds for the detection of a gap in noise. This work has implications for understanding the effects of amplification on the ability to perceive temporal cues in speech.
Verification and validation are objective and subjective measurements of hearing aid function. Many studies have provided rationales for performing these measurements as necessary for hearing aid practitioners to provide the highest level of care. Several researchers have suggested that completing these measurements as part of routine clinical care will reduce the number of return visits, reduce the number of aids returned for credit, and increase patient satisfaction. The purpose of this review article is to provide background, method and rationale for practitioners to use these measurements to improve their practice of hearing healthcare.
Abstract Objective: To investigate the predicted threshold shift associated with the use of nonlinear hearing aids fitted to the NAL-NL2 or the DSL m[i/o] prescription for children with the same audiograms. For medium and high input levels, we asked: (1) How does predicted asymptotic threshold shifts (ATS) differ according to the choice of prescription? (2) How does predicted ATS vary with hearing level for gains prescribed by the two prescriptions? Design: A mathematical model consisting of the modified power law combined with equations for predicting temporary threshold shift (Macrae, 1994b) was used to predict ATS. Study sample: Predicted threshold shift were determined for 57 audiograms at medium and high input levels. Results: For the 57 audiograms, DSL m[i/o] gains for high input levels were associated with increased risk relative to NAL-NL2. The variation of ATS with hearing level suggests that NAL-NL2 gains became unsafe when hearing loss > 90 dB HL. The gains prescribed by DSL m[i/o] became unsafe when hearing loss > 80 dB HL at a medium input level, and > 70 dB HL at a high input level. Conclusion: There is a risk of damage to hearing for children using nonlinear amplification. Vigilant checking for threshold shift is recommended.
In congenital visual impaired individuals one modality is impaired (visual modality) this impairment is compensated by other sensory modalities. There is evidence that visual impaired performed better in different auditory task like localization, auditory memory, verbal memory, auditory attention, and other behavioural tasks when compare to normal sighted individuals.
The current study was aimed to compare the temporal resolution, frequency resolution and speech perception in noise ability in individuals with congenital visual impaired and normal sighted.
Temporal resolution, frequency resolution, and speech perception in noise were measured using MDT, GDT, DDT, SRDT, and SNR50 respectively. Twelve congenital visual impaired participants with age range of 18 to 40 years were taken and equal in number with normal sighted participants. All the participants had normal hearing sensitivity with normal middle ear functioning.
Individual with visual impairment showed superior threshold in MDT, SRDT and SNR50 as compared to normal sighted individuals. This may be due to complexity of the tasks; MDT, SRDT and SNR50 are complex tasks than GDT and DDT.
Visual impairment showed superior performance in auditory processing and speech perception with complex auditory perceptual tasks.
There are two methods for adjusting the characteristics of hearing aids for individuals with impaired hearing: a comparative procedure and a prescriptive procedure. In practice, these two procedures are usually combined at hearing aid clinics. At present, the NAL-NL (National Acoustic Laboratory-nonlinear) and the DSL (Desired Sensation Level) procedures are generally used worldwide. Although no significant differences in speech perception have been seen between the NAL-NL and the DSL in several investigations, the DSL results in a loud sensation more often than the NAL-NL. The prescriptive target indicated by these procedures should be accomplished at the end stage of fitting, rather than at the start. For new hearing aid users, a procedure that starts with less acoustic gain and gradually reaches the final prescriptive target gain has been proposed. Investigating whether these prescriptive processes developed in English-speaking countries are valid for use in Japan will be important.
This study examined the influence of prescription on hearing aid (HA) fitting characteristics and 5-year developmental outcomes of children.
A randomised controlled trial implemented as part of a population-based study on Longitudinal Outcomes of Children with Hearing Impairment (LOCHI).
Two-hundred and thirty-two children that were fit according to either the National Acoustic Laboratories (NAL) or Desired Sensation Level (DSL) prescription.
Deviation from targets and root-mean-square error in HA fitting revealed no significant difference between fitting prescriptions. Aided audibility quantified by using the Speech Intelligibility Index (SII) model showed that DSL provided higher audibility than NAL at low and medium input levels but not at high input level. After allowing for hearing loss desensitisation, differences in audibility between prescription groups were significant only at low input level. The randomised trial of prescription that was implemented for 163 children revealed no significant between-group differences in speech production, perception, and language; but parent-rated functional performance was higher for the DSL than for the NAL group.
Proximity to prescriptive targets was similar between fitting prescriptions. The randomised trial revealed differences in aided audibility at low input level between prescription groups, but no significant differences in speech and language abilities.
We investigated the factors influencing speech perception in babble for 5-year-old children with hearing loss who were using hearing aids (HAs) or cochlear implants (CIs).
Speech reception thresholds (SRTs) for 50% correct identification were measured in two conditions - speech collocated with babble, and speech with spatially separated babble. The difference in SRTs between the two conditions give a measure of binaural unmasking, commonly known as spatial release from masking (SRM). Multiple linear regression analyses were conducted to examine the influence of a range of demographic factors on outcomes.
Participants were 252 children enrolled in the Longitudinal Outcomes of Children with Hearing Impairment (LOCHI) study.
Children using HAs or CIs required a better signal-to-noise ratio to achieve the same level of performance as their normal-hearing peers but demonstrated SRM of a similar magnitude. For children using HAs, speech perception was significantly influenced by cognitive and language abilities. For children using CIs, age at CI activation and language ability were significant predictors of speech perception outcomes.
Speech perception in children with hearing loss can be enhanced by improving their language abilities. Early age at cochlear implantation was also associated with better outcomes.
The purpose of this study was to develop lists of stories for the auditory training and to evaluate the effect of 10-week auditory training using developed stories for hearing-impaired listeners.
A total of fifty-five stories and related subjective and objective questions were developed. In order to validate the training materials, thirty-two participants examined the familiarity of stories, the interest of stories, the difficulty of sentences, the familiarity of words and the difficulty of questions. According to the validation results, the stories were revised and recorded by a professional female speaker. For determining the efficacy of auditory training using developed stories, fifteen hearing-impaired listeners participated. Among them, eight subjects (auditory training group) received the 40-minute, once per a week for 10-week auditory training, and seven control subjects (non-training group) did not receive any auditory training. Sentence recognition scores with and without noise and Korean version of international outcome inventory for hearing aids (KIOI-HA) were evaluated at before and after the auditory training. Non-training group underwent the same battery of tests at the same time intervals equivalent to the training group.
Results showed that the auditory training enhanced sentence recognition in quiet as well as in noise conditions. Also, there was positive impacts of training on the results of K-IOI-HA.
These results suggested that the 10-week auditory training using the stories is useful to improve speech understanding of hearing aid users as well as their subjective satisfaction on hearing aids.
The general goal of providing amplification is to improve functional auditory capacity and restore good communication skills. Amplification should restore the audibility of soft sounds, provide improved intelligibility of speech at conversational listening levels, and ensure that intense sounds are not amplified to an uncomfortably loud level. There are several prescription methods that provide frequency-specific target values for soft, conversational, and intense sounds. Despite differences in the target values, no validated prescription method has been clearly shown to be superior to any of the other methods in terms of patient benefit (e.g., greater satisfaction, less residual disability). However, clinical studies have clearly shown that when a well-researched prescriptive approach is used and appropriate gain is delivered across frequencies, speech intelligibility is enhanced, and there is improved patient benefit and satisfaction. There is also irrefutable evidence that the audiologist can improve the match to the prescription target values using a probe microphone placed within the patient’s ear canal. As a result, carefully conducted verification is an essential component of long-term success with amplification. The most recent generation of prescription methods provides a degree of personalization to the target values beyond that associated with hearing threshold levels. However, there is an urgent clinical need to address the wide range of clinical outcomes that occur in hearing aid users with apparently similar characteristics.
The size of the conductive hearing loss of subjects with conductive and mixed hearing impairment was compared with the insertion gain of the hearing aids used by them. Conductive impairment does not cause loudness tolerance problems so people with conductive and mixed hearing impairment might be expected to choose to use gain which fully compensates for their conductive loss. The results do not support this expectation but rather confirm the observation made by others that the gain used fails well short of that required to fully compensate for the loss. It is suggested that this may be at least partly due to an inadequate maximum output of the hearing aids being used by some of the subjects. If this explanation is confirmed the results obtained will be specific to the particular hearing aid, and therefore unsuitable as a basis for a general selection procedure.
NAL-NL2 is the second generation of prescription procedures from
The National Acoustic Laboratories (NAL) for fitting wide dynamic
range compression (WDRC) instruments. Like its predecessor NALNL1
(Dillon, 1999), NAL-NL2 aims at making speech intelligible and
overall loudness comfortable. This aim is mainly driven by a belief that
these factors are most important for hearing aid users, but is also driven
by the fact that less information is available about how to adjust
gain to optimise other parameters that affect prescription such as
localisation, tonal quality, detection of environmental sounds, and naturalness.
In both formulas, the objective is achieved by combining a
speech intelligibility model and a loudness model in an adaptive computer-
controlled optimisation process. Adjustments have further been
made to the theoretical component of NAL-NL2 that are directed by
empirical data collected during the past decade with NAL-NL1. In this
paper, the data underlying NAL-NL2 and the derivation procedure are
presented, and the main differences from NAL-NL1 are outlined.
The goal of this study is to model the effect of sensorineural hearing impairment on loudness perception for stationary stimuli of variable bandwidth. Loudness growth functions were obtained employing a categorical scaling technique with 10 categories. Loudness scaling was performed with 9 normal‐hearing and 14 sensorineural hearing‐impaired subjects employing bandfiltered noises with bandwidths between 1–6 critical bands. For normal‐hearing listeners, categorical scaling revealed similar differences across stimulus conditions as with loudness balancing. The loudness functions of the hearing‐impaired listeners show both, a steeper increase (recruitment) and reduced loudness summation. Both aspects were successfully modeled by Zwicker’s loudnessmodel with three extensions to take account of hearing impairment. Raised audiometric threshold is modeled by a frequency‐dependent attenuation after calculation of excitation patterns. Increasing the exponent in calculating the specific loudness yields recruitment. Reduced frequency selectivity is accounted for by the normal dependence of filter bandwidth on level in the excitation patterns. The extended model describes well the measured individual loudness growth functions of hearing‐impaired subjects for stimuli of differing bandwidth.
Chapter 1 - The physiology and function of the normal and damaged cochlea Chapter 2 - Absolute thresholds and frequency selectivity in normal and impaired hearing Chapter 3 - Loudness perception and intensity resolution in people with normal and impaired hearing Chapter 4 - Effects of cochlear damage on temporal resolution and temporal integration Chapter 5 - Pitch perception and frequency discrimination in normally hearing and hearing-impaired people Chapter 6 - Sound localization and binaural hearing in normal and hearing-impaired people Chapter 7 - Speech perception by people with cochlear damage Chapter 8 - Limitations and potentials of hearing aids
The long-term average speech spectrum (LTASS) and some dynamic characteristics of speech were determined for 12 languages: English (several dialects), Swedish, Danish, German, French (Canadian), Japanese, Cantonese, Mandarin, Russian, Welsh, Singhalese, and Vietnamese. The LTASS only was also measured for Arabic. Speech samples (18) were recorded, using standardized equipment and procedures, in 15 localities for (usually) ten male and ten female talkers. All analyses were conducted at the National Acoustic Laboratories, Sydney. The LTASS was similar for all languages although there were many statistically significant differences. Such differences were small and not always consistent for male and female samples of the same language. For one-third octave bands of speech, the maximum short-term rms level was 10 dB above the maximum long-term rms level, consistent across languages and frequency. A ''universal'' LTASS is suggested as being applicable, across languages, for many purposes including use in hearing aid prescription procedures and in the Articulation Index.
This paper describes the speech and noise material on a new set of three CDs that is considered very suitable for hearing assessment and fine-tuning of hearing aids in audiological clinics. The material includes continuous discourses, various background noises, and three different speech test materials (BKB sentence test, four SPIN sentence lists, and Vowel-Consonant-Vowel (VCVs) nonsense syllables). All speech samples are recorded using native speakers of Australian English. Normative data in the form of the central part of performance-intensity functions are presented for the BKB sentences in babble-noise and for intelligibility rating of continuous discourse in nine background noises together with list-equivalence data for the BKB test. For each test, the critical difference that needs to be exceeded to obtain significantly different results is also presented. Applications for the material with respect to candidacy and hearing aid fine-tuning are discussed.
Zwicker's loudness model has the following stages: (a) A fixed filter representing transfer through the outer and middle ear; (b) Calculation of an excitation pattern from the physical spectrum; (c) Transformation of the excitation pattern to a specific loudness pattern. The area under the specific loudness pattern is assumed to determine loudness. This paper presents some modifications and extensions to Zwicker's loudness model. Changes are made in: (a) The assumed transfer function for the outer and middle ear; (b) The way that excitation patterns are calculated; (c) The way that specific loudness is related to excitation for sounds in quiet and in noise. The revised model accounts more accurately than Zwicker's model for the way that equal-loudness contours change with level. It also provides a more satisfactory explanation of why the loudness of a sound of fixed intensity remains constant when the sound has a bandwidth less than the critical bandwidth (CB). Finally, the revised model is able to account for the loudness of partially masked sounds without the introduction of correction factors. The revised model has the advantage that the excitation patterns on which it is based are calculated from analytical formulae rather than by reference to charts or tables. This avoids discontinuities in the predicted values of loudness.
A procedure is described for determining the gain requirements as a function of frequency for persons who have sensorineural hearing impairments. It is based on delivering sounds at preferred listening levels which are estimated from hearing threshold levels. Adjustments are incorporated in the procedure so that all frequency components of a speech signal will be presented with approximately equal loudness, thus enabling the maximum amount of speech signal to be delivered without exceeding comfort level in any frequency region. Special advantages of the procedure are that it is more widely applicable than many others and that the final selection is in terms of real-ear gain measured with the selected hearing aid being wom by the individual.
A clinical trial of Oticon DigiFocus hearing aid was performed. The test aid was evaluated on 33 subjects with several years' experience as users of modern analog hearing aids. These aids were used as reference for the 1-month-long trial. The Abbreviated Profile of Hearing Aid Benefit (APHAB) showed a mean difference in benefit with superior ratings for the test aid concerning ease of communication, speech in reverberation and speech in background noise. The subjects' own aids were rated somewhat better concerning aversiveness of sounds, but this difference was not statistically significant. The Gothenburg Profile showed a statistically significant difference between the test aid and the reference aids in favour of the test aid. The difference was not most evident with regard to speech communication and the effects of hearing loss on social interactions. Sound quality ratings concerning clearness were significantly higher for the test aid. Speech recognition thresholds in noise were on average 0.7 dB better for the test aids when tested at speech levels 60 and 75 dB. The difference was statistically significant only at 75 dB. There was significant interaction between general preference and hearing aid type, indicating that overall sound quality was an important factor affecting the general preference for either the test aid or the reference aid. Twenty-three subjects generally preferred the test aid, six preferred their own aid and four stated no difference.
This paper describes a preliminary laboratory-based evaluation of a method for fitting hearing aids with an extended high-frequency response, called CAMEQ2-HF. Linear filtering was used to implement the CAMEQ2-HF-prescribed gains for speech with an input level of 65 dB SPL. The results obtained using four normal-hearing (NH) and fifteen hearing-impaired (HI) listeners showed: (1) The gains were sufficient to make components above 5 kHz audible when those components were presented alone, and when they were presented together with the lower-frequency components; (2) NH listeners preferred a wider bandwidth (10 or 7.5 kHz versus 5 kHz) for both pleasantness and speech clarity, while HI listeners usually preferred a narrower bandwidth for pleasantness but a wider bandwidth for clarity; (3) HI listeners performed better on the ‘S-test (detection of word-final /s/ or /z/) with a wider than with a narrower bandwidth (7.5 versus 5 kHz); (4) Identification of vowel-consonant-vowel nonsense syllables improved with increasing bandwidth from 5 to 7.5 kHz for the NH but not for the HI listeners.
A method for fitting multichannel compression hearing aids with an extended high-frequency response, called CAMEQ2-HF, was described by . This study describes an evaluation of the method, using a 16-channel behind the ear hearing aid incorporating slow-acting compression and providing gain for frequencies up to 7500 Hz.
Eleven participants with mild to moderate cochlear hearing loss were fitted bilaterally using the gains prescribed by CAMEQ2-HF. The fittings were checked using real-ear measurements with swept sinusoidal signals, and adjustments were made so that the target gains at the center frequency of each channel were achieved with a typical tolerance of +/-3 dB for an input level of 65 dB and with a typical tolerance of +/-5 dB for levels of 50 and 80 dB SPL. Participants were asked to wear the hearing aids as much as possible in their everyday lives and to fill in questionnaires and a structured diary about their experience of loudness and their listening problems in everyday life, both for listening unaided and after a period of use of the aids.
Scores obtained using the Profile of Aided Loudness (PAL) indicated that the hearing aids led to a clear increase in loudness (relative to unaided listening) for weak sounds and to smaller increases in loudness for sounds of medium and high intensity. For aided listening, strong sounds were typically rated as "loud, but OK." Satisfaction ratings for loudness obtained using the PAL showed only small differences between unaided and aided listening. Responses obtained via the structured diary (for aided listening only) indicated that target speech was usually judged as "loud enough" in a variety of situations. Clarity judgments ranged from "reasonably clear" to "OK" for most situations, but fell to "not very clear" for a noisy group situation. The loudness of background sounds was mostly judged as "OK," except for the noisy group situation in which the background was judged "bit loud." Results from the Abbreviated Profile of Hearing-Aid Benefit questionnaire indicated fewer problems with "ease of communication," "reverberation," and "background noise" for aided than for unaided listening, but more problems with "aversiveness." Nine of 11 ratings of overall sound quality fell in the categories "satisfied" or "very satisfied."
The CAMEQ2-HF fitting method generally led to satisfactory loudness and sound quality in everyday life for people with mild to moderate hearing loss.
This study evaluated how closely the DSL v5.0 a prescription could be approximated with hearing aids, its relationship to preferred listening levels (PLLs) of adults with acquired hearing loss, and the self-reported outcomes of the resulting fittings.
Thirty adults with varying degrees and configurations of hearing loss ranging from mild to severe.
Hearing aid output was measured after the initial fitting to DSL v5.0 a targets and after determination of the PLL after approximately 90 days. The Client Oriented Scale of Improvement (COSI) was used to evaluate outcome.
The 95% confidence interval of fits to target ranged from 5.8 to 8.4 dB across frequency. The DSL v5.0 a adult algorithm approximated the PLLs of the participants within 2.6 dB on average. Hearing aid fittings provided positive subjective outcome improvements on the COSI.
Findings suggest that the use of DSL v5.0 a for the fitting of hearing aids on adults with acquired hearing loss was feasible and provided an appropriate initial fitting.
Moore et al (1999b) described a procedure, CAMEQ, for the initial fitting of multi-channel compression hearing aids. The procedure was derived using a model of loudness perception for impaired hearing. We describe here the development of a new fitting method, CAMEQ2-HF, which differs from CAMEQ in the following ways: (1) CAMEQ2-HF gives recommended gains for centre frequencies up to 10 kHz, whereas the upper limit for CAMEQ is 6 kHz; (2) CAMEQ is based on the assumption that the hearing aid user faces the person they wish to hear and uses a free-field-to-eardrum transfer function for frontal incidence. CAMEQ2-HF is based on the assumption that the user may wish to hear sounds from many directions, and uses a diffuse-field-to-eardrum transfer function; (3) CAMEQ2-HF is based on an improved loudness model for impaired hearing; (4) CAMEQ2-HF is based on recent wideband measurements of the average spectrum of speech.
The overall level of a sound is an important auditory cue to distance in rooms, but this cue might be affected adversely by the amplitude compression found in most modern hearing aids because this explicitly changes levels. This prediction was tested using a synthetic-distance design to measure the just-noticeable difference (JND) in distance from distances of 2 or 5 m. Twenty-six aided listeners participated. The results did not show any effect of compression ratio upon JNDs. A possible interpretation is that the listeners had acclimatized to the effect their aids have on level.
While there have been many studies of real-world preferred hearing aid gain, few data are available from participants using hearing aids with today's special features activated. Moreover, only limited data have been collected regarding preferred gain for individuals using trainable hearing aids.
To determine whether real-world preferred hearing aid gain with trainable modern hearing aids is in agreement with previous work in this area, and to determine whether the starting programmed gain setting influences preferred gain outcome.
An experimental crossover study. Participants were randomly assigned to one of two treatment groups. Following initial treatment, each subject crossed to the opposite group and experienced that treatment.
Twenty-two adults with downward sloping sensorineural hearing loss served as participants (mean age 64.5; 16 males, 6 females). All were experienced users of bilateral amplification.
Using a crossover design, participants were fitted to two different prescriptive gain conditions: VC (volume control) start-up 6 dB above NAL-NL1 (National Acoustic Laboratories-Non-linear 1) target or VC start-up 6 dB below NAL-NL1 target. The hearing aids were used in a 10 to 14 day field trial for each condition, and using the VC, the participants could "train" the overall hearing aid gain to their preferred level. During the field trial, daily hearing aid use was logged, as well as the listening situations experienced by the listeners based on the hearing instrument's acoustic scene analysis. The participants completed a questionnaire at the start and end of each field trial in which they rated loudness perceptions and their satisfaction with aided loudness levels.
Because several participants potentially experienced floor or ceiling effects for the range of trainable gain, the majority of the statistical analysis was conducted using 12 of the 22 participants. For both VC-start conditions, the trained preferred gain differed significantly from the NAL-NL1 prescriptive targets. More importantly, the initial start-up gain significantly influenced the trained gain; the mean preferred gain for the +6 dB start condition was approximately 9 dB higher than the preferred gain for the -6 dB start condition, and this difference was statistically significant (p < .001). Partial eta squared (n2) = 0.919, which is a large effect size. Deviation from the NAL-NL1 target was not significantly influenced by the time spent in different listening environments, amount of hearing aid use during the trial period, or amount of hearing loss. Questionnaire data showed more appropriate ratings for loudness and higher satisfaction with loudness for the 6 dB below target VC-start condition.
When trainable hearing aids are used, the initial programmed gain of hearing instruments can influence preferred gain in the real world.
Self-adjustments of variable hearing aid parameters are essential for trainable hearing aids to provide customized amplification for different listening environments. Prompted by a finding of Dreschler et al. [Ear Hear. 29, 214-227 (2008)], this study investigates the effect of the base line (starting) response on self-adjustments of gain in different frequency bands. In a laboratory test, 24 hearing-impaired listeners adjusted the bass, treble, and overall gain to reach their preferred responses from two different base line responses for 12 different listening situations. The adjustments were repeated five times using the preferred response after each adjustment as base line response for the next adjustment. Half of the listeners further compared three different response shapes, within the range of preferred responses, pairwise ten times for preferential and perceptual discrimination. The results revealed that base line response biases were more pronounced at low frequencies and for listeners with a flat hearing loss configuration. While 83% of listeners reliably discriminated between the average selected biased responses, only 25% demonstrated reliable preferences for one response over the other. Listeners who showed preferential discrimination ability were those who were less biased by the base line response. The clinical implication is that self-adjustments should begin from an appropriately prescribed starting response.
It is possible for auditory prostheses to provide amplification for frequencies above 6 kHz. However, most current hearing-aid fitting procedures do not give recommended gains for such high frequencies. This study was intended to provide information that could be useful in quantifying appropriate high-frequency gains, and in establishing the population of hearing-impaired people who might benefit from such amplification.
The study had two parts. In the first part, wide-bandwidth recordings of normal conversational speech were obtained from a sample of male and female talkers. The recordings were used to determine the mean spectral shape over a wide frequency range, and to determine the distribution of levels (the speech dynamic range) as a function of center frequency. In the second part, audiometric thresholds were measured for frequencies of 0.125, 0.25, 0.5, 1, 2, 3, 4, 6, 8, 10, and 12.5 kHz for both ears of 31 people selected to have mild or moderate cochlear hearing loss. The hearing loss was never greater than 70 dB for any frequency up to 4 kHz.
The mean spectrum level of the speech fell progressively with increasing center frequency above about 0.5 kHz. For speech with an overall level of 65 dB SPL, the mean 1/3-octave level was 49 and 37 dB SPL for center frequencies of 1 and 10 kHz, respectively. The dynamic range of the speech was similar for center frequencies of 1 and 10 kHz. The part of the dynamic range below the root-mean-square level was larger than reported in previous studies. The mean audiometric thresholds at high frequencies (10 and 12.5 kHz) were relatively high (69 and 77 dB HL, respectively), even though the mean thresholds for frequencies below 4 kHz were 41 dB HL or better.
To partially restore audibility for a hearing loss of 65 dB at 10 kHz would require an effective insertion gain of about 36 dB at 10 kHz. With this gain, audibility could be (partly) restored for 25 of the 62 ears assessed.
The application of the articulation index (AI) model to the fitting of linear amplification was evaluated for 12 subjects with sensorineural hearing loss. Comparisons were made of amplification characteristics specified by the NAL (Byrne & Dillon, 1986) and POGO (McCandless & Lyregaard, 1983) prescriptions, as well as a procedure that attempted to maximize the AI (AIMax). For all subjects, the relationship between percent-correct scores on a nonsense syllable test and AIs was monotonic for the two prescriptions, indicating that the AI was effective for comparing conditions typical of those recommended clinically. However, subjects having sloping high-frequency hearing losses demonstrated nonmonotonicity due to poor performance in the AIMax condition. For these subjects, the AIMax condition required much more gain at high than at low frequencies, circumstances that Skinner (1980) warned will cause less-than-optimal performance for individuals having sloping high-frequency hearing loss.
This paper describes the first phase in the development of the Connected Speech Test (CST). This test of intelligibility of everyday speech has been developed primarily for use as a criterion measure in investigations of hearing aid benefit. The test consists of 48 passages of conversationally produced connected speech. Each passage contains 25 key words for scoring. All passages are of equal intelligibility for the average normal hearer. Key words vary in intelligibility within a passage but span the same intelligibility range in all passages. Several passages are administered, and the results averaged, to yield a single intelligibility score. For pairs of scores, each based on mean performance across 4 randomly-chosen passages, the 95% critical difference is estimated to be about 14 rationalized arcsine units (rau). The performance-intensity function for the CST has a slope of 12 rau/dB signal-to-babble ratio. Investigations of the test are continuing with hearing-impaired listeners.
A new procedure is presented for selecting the gain and frequency response of a hearing aid from pure-tone thresholds. This was developed from research which showed that a previous procedure did not meet its aim of amplifying all frequency bands of speech to equal loudness but that frequency responses which did so were considerably more effective. Measurements of 30 sensorineurally hearing-impaired ears (27 subjects), together with data from other studies, were analyzed to determine the best formula for predicting the optimal frequency response, for each individual, from the audiogram. The analysis indicated that a flat audiogram would require a rising frequency response characteristic of about 8 dB/octave up to 1.25 kHz and thereafter a falling characteristic of about 2 dB/octave. Variations in audiogram slope required about one-third as much variation in response slope. Three frequency average (3FA) gain was calculated to equal the 3FA gain of the previous procedure. Forty-four subjects (67 aided ears) fitted by the new procedure were evaluated by paired comparison judgments of the intelligibility and pleasantness of speech. The prescribed frequency response was seldom inferior to, and usually better than, any of several variations having more, or less, low and/or high-frequency amplification. On the average, used gain was approximately equal to prescribed gain. It is concluded that the new formula should prescribe a near optimal frequency response with few exceptions.
Frequency response characteristics were selected for 14 hearing-impaired ears, according to six procedures. Three procedures were based on MCL measurements with speech bands of three bandwidths (1/3 octave, 1 octave, and 1 2/3 octaves). The other procedures were based on hearing thresholds, pure-tone MCLs, and pure-tone LDLs. The procedures were evaluated by speech discrimination testing, using nonsense syllables in noise, and by paired comparison judgments of the intelligibility and pleasantness of running speech. Speech discrimination testing showed significant differences between pairs of responses for only seven test ears. Nasals and glides were most affected by frequency response variations. Both intelligibility and pleasantness judgments showed significant differences for all test ears. Intelligibility in noise was less affected by frequency response differences than was intelligibility in quiet or pleasantness in quiet or in noise. For some ears, the ranking of responses depended on whether intelligibility or pleasantness was being judged and on whether the speech was in quiet or in noise. Overall, the three speech band MCL procedures were far superior to the others. Thus the studies strongly support the frequency response selection rationale of amplifying all frequency bands of speech to MCL. They also highlight some of the complications involved in achieving this aim.
Measurements were made of the effects of stimulus bandwidth and type (speech bands versus pure tones) on interfrequency differences at the most comfortable loudness level (MCL). The MCLs were measured for speech bands of three bandwidths (1/3 octave, 1 octave, and 1 2/3 octaves) at three frequencies (0.4 kHz, 1.25 kHz, and 3.15 kHz) for 11 sensorineurally hearing-impaired subjects (14 test ears). The MCLs were also measured with pulsed pure tones. It was found that bandwidth and stimulus type both had significant effects on interfrequency differences in MCLs. Also, the mean speech band MCLs were significantly higher than the mean pure-tone MCLs. A subsidiary experiment suggested that, when bands of speech from different frequency regions are all presented at MCL, they will be approximately, but not precisely, equal in loudness. The findings have implications for hearing aid selection procedures because most aim to amplify all frequency bands of speech to MCL, or equal loudness at a comfortable level. The use of different types or bandwidths of test stimuli would result in substantially different frequency response prescriptions in some cases.
There is a growing trend for hearing aids to incorporate wide dynamic range compression. The input/output (I/O) hearing aid formula, presented in this report, is a general frequency-specific mathematical approach which describes the relationship between the input level of a signal delivered to a hearing aid and the output level produced by the hearing aid. The I/O formula relates basic psychoacoustic parameters, including hearing threshold level and uncomfortable listening level, to the electroacoustic characteristics of hearing aids. The main design goal of the I/O formula was to fit the acoustic region corresponding to the "extended" normal auditory dynamic range into the hearing-impaired individual's residual auditory dynamic range. The I/O approach can be used to fit hearing aids utilizing linear gain, linear compression or curvilinear compression to a hearing-impaired individual's residual auditory area.
Recently, band importance functions have been developed for a number of speech tests used in audiology. These functions, as well as the importance functions for average (everyday) speech, are also being considered for the inclusion in the revised Articulation Index standard (submitted for vote to the Acoustical Society of America). In this paper, the band importance functions for different speech materials (usually reported in literature for 1/3 octave bands) have been recalculated to correspond to frequency bands normally used in audiological applications. In addition, criteria for selecting appropriate importance functions and transfer functions are discussed.
In a series of experiments with a wearable binaural digital hearing aid, two hearing aid processing algorithms were compared. Both algorithms provided individual frequency shaping via a seven-band filterbank with compression limiting in the high-frequency channel. They differed in the processing of the low-frequency channel, using dynamic range compression for one (DynEar) and linear processing with compression limiting for the other (LinEar). In a pilot field test we found that LinEar/ DynEar preference based on use time could be predicted from auditory dynamic range data. For the subjects who preferred DynEar, the mean dynamic range was broader for low and mid frequencies and narrower for high frequencies, as compared with the LinEar preference subjects. These groupings were tested as predictors of user preference and performance in a main field test.
The main study included 26 hearing aid users with symmetrical sensorineural losses. The algorithms were compared in a one-mo-long blind field test. A data logger function was included for objective recording of the total time each algorithm was used and how the volume controls were used. The preference was based on the time used for each algorithm and on subjective statements. Threshold signal-to-noise ratio (S/N-threshold) for speech was tested, and sound quality ratings were obtained through a questionnaire. We also tested the S/N-thresholds for the subjects' conventional (own) aids.
The preference was correctly predicted by the dynamic range data on 12 out of 15 new cases. S/N-thresholds were lower for the preferred fittings compared with the nonpreferred fittings and with the subjects' own aids. In the questionnaire the preferred fittings were rated significantly higher in terms of overall impression and clearness. Because of the systematic way the DynEar-preference subjects adjusted the high-frequency DynEar gain, we speculate that upward spread of masking may have been a factor in preference and performance. Additionally, LinEar-preference subjects' preference and performance might have been influenced by excessive compression ratios with the DynEar processing in these cases.
1. Preference for DynEar versus LinEar depends on the auditory dynamic range. 2. S/N-thresholds for speech were better for the preferred fittings, which also were rated higher in terms of overall impression of sound quality and clearness.
Two fitting algorithms for linear hearing aids were compared using a wearable digital hearing aid in a one-month blind field test: a prescriptive method (POGO II) and a new algorithm, LinEar. Both used seven bands for frequency shaping, and two channel compression limiting. When fitting LinEar, the subjects individually adjusted the frequency response according to specified criteria. LinEar used a lower compression threshold setting than prescribed by POGO II. Eight subjects tested the two algorithms in a one-months blind field test as well as in the laboratory. The individual LF- and HF-gain adjustments of the frequency response in LinEar showed rather large variations compared to the POGO II prescription. Measures of S/N for speech did not show any significant differences between LinEar and POGO II, while overall sound quality ratings in laboratory and field test showed that LinEar was rated significantly higher than POGO II.
Three digital signal processing algorithms named RangeEar, DynEar, and LinEar were compared with regard to user preference and performance when a wearable digital filterbank hearing aid was used. All three algorithms provided individual frequency shaping via a seven-band filterbank. Compression was used in a low-frequency (LF) and a high-frequency (HF) channel. RangeEar and DynEar used wide dynamic range syllabic compression in the LF channel, whereas LinEar used compression limiting. In the HF channel, RangeEar used a slow acting automatic volume control, whereas DynEar and LinEar used compression limiting. The subjects had access to a manual volume control when using the LinEar or DynEar options.
The study included 13 hearing aid users with symmetrical sensorineural losses. In a 1 mo long blind field test, the RangeEar algorithm was compared with the preferred algorithm from an earlier study, DynEar or LinEar. A data logger function was included for objective recording of the total time each algorithm was used and how the volume controls were used. The preference was based on the time used for each algorithm and from subjective statements. Threshold signal-to-noise ratio (S/N-threshold) for speech was tested, and sound quality ratings were obtained through a questionnaire.
Of the 13 subjects, six preferred the RangeEar fitting and another four preferred the DynEar fitting. Two subjects preferred the LinEar fitting and one had equal preference for RangeEar and LinEar. The results from the questionnaire showed that the preferred fittings were rated higher concerning overall impression of sound quality and clearness, whereas the S/N for the speech test did not show any differences. Preferences, where stated, could be predicted from auditory dynamic range measurements in the LF and HF frequency ranges. The mean dynamic range was broader for low and narrower for high frequencies for those who preferred the RangeEar or DynEar fitting as compared with those who preferred the LinEar fitting. The preference between RangeEar and DynEar was predicted by differences in the HF range, with the narrower dynamic range for the DynEar preference subjects.
Most subjects preferred the option of having a wide dynamic range syllabic compressor in the LF channel and having the overall gain in the HF channel adjustable, either manually (DynEar) or automatically (RangeEar).
Two experiments were conducted to examine the relationship between audibility and speech recognition for individuals with sensorineural hearing losses ranging from mild to profound degrees. Speech scores measured using filtered sentences were compared to predictions based on the Speech Intelligibility Index (SII). The SII greatly overpredicted performance at high sensation levels, and for many listeners, it underpredicted performance at low sensation levels. To improve predictive accuracy, the SII needed to be modified. Scaling the index by a multiplicative proficiency factor was found to be inappropriate, and alternative modifications were explored. The data were best fitted using a method that combined the standard level distortion factor (which accounted for decrease in speech intelligibility at high presentation levels based on measurements of normal-hearing people) with individual frequency-dependent proficiency. This method was evaluated using broadband sentences and nonsense syllables tests. Results indicate that audibility cannot adequately explain speech recognition of many hearing-impaired listeners. Considerable variations from audibility-based predictions remained, especially for people with severe losses listening at high sensation levels. The data suggest that, contrary to the basis of the SII, information contained in each frequency band is not strictly additive. The data also suggest that for people with severe or profound losses at the high frequencies, amplification should only achieve a low or zero sensation level at this region, contrary to the implications of the unmodified SII.
The present study was a systematic investigation of the benefit of providing hearing-impaired listeners with audible high-frequency speech information. Five normal-hearing and nine high-frequency hearing-impaired listeners identified nonsense syllables that were low-pass filtered at a number of cutoff frequencies. As a means of quantifying audibility for each condition, Articulation Index (AI) was calculated for each condition for each listener. Most hearing-impaired listeners demonstrated an improvement in speech recognition as additional audible high-frequency information was provided. In some cases for more severely impaired listeners, increasing the audibility of high-frequency speech information resulted in no further improvement in speech recognition, or even decreases in speech recognition. A new measure of how well hearing-impaired listeners used information within specific frequency bands called "efficiency" was devised. This measure compared the benefit of providing a given increase in speech audibility to a hearing-impaired listener to the benefit observed in normal-hearing listeners for the same increase in speech audibility. Efficiencies were calculated using the old AI method and the new AI method (which takes into account the effects of high speech presentation levels). There was a clear pattern in the results suggesting that as the degree of hearing loss at a given frequency increased beyond 55 dB HL, the efficacy of providing additional audibility to that frequency region was diminished, especially when this degree of hearing loss was present at frequencies of 4000 Hz and above. A comparison of analyses from the "old" and "new" AI procedures suggests that some, but not all, of the deficiencies of speech recognition in these listeners was due to high presentation levels.
A model for predicting loudness for people with cochlear hearing loss is applied to the problem of the initial fitting of multi-channel fast-acting compression hearing aids. The fitting is based entirely on the pure tone audiogram, and does not require measures of loudness growth. One constraint is always applied: the specific loudness pattern evoked by speech of a moderate level (65 dB SPL) should be reasonably flat (equal loudness per critical band), and the overall loudness should be similar to that evoked in a normal listener by 65-dB speech. This is achieved using the 'Cambridge' formula. For hearing aids where the compression threshold in each channel can be set to a very low value, an additional constraint is used: speech with an overall level of 45 dB SPL should be audible over its entire dynamic range in all frequency channels from 500 Hz up to about 4 kHz. For hearing aids where the compression thresholds cannot be set to very low values, a different additional constraint is used: the specific loudness pattern evoked by speech of a high level (85 dB SPL, and with the spectral characteristics of shouted speech) should be reasonably flat, and the overall loudness should be similar to that evoked in a normal listener by 85-dB speech. For both cases, compression ratios are limited to values below 3. For each of these two cases, we show how to derive compression ratios and gains, and for the first case, compression thresholds, for each channel. The derivations apply to systems with any number of channels. A computer program implementing the derivations is described. The program also calculates target insertion gains at the centre frequency of each channel for input levels of 50, 65 and 80 dB SPL, and target gains at the eardrum measured relative to the level at the reference microphone of a probe microphone system.
This project examined the effect of varying compression ratio on speech recognition and quality. Both listeners with mild-to-moderate sensorineural hearing loss and a control group of listeners with normal hearing participated. Test materials were sentences from the Connected Speech Test (R. M. Cox, G. C. Alexander, & C. Gilmore, 1987) which were digitally processed with linear amplification and wide dynamic range compression amplification with 3 compression ratios. Speech-recognition scores were obtained with sentences in quiet and in noise at a 10-dB signal-to-noise ratio for each amplification condition. Additionally, the participants rated each amplification condition in terms of clarity, pleasantness, ease of understanding, and overall impression. Results indicated that, for speech in quiet, compression ratio had no effect on speech-recognition scores; however, speech-quality ratings decreased as compression ratio increased. For speech in noise, both speech-recognition scores and ratings decreased with increasing compression ratio for the listeners with hearing loss. These results suggest that selection of compression ratio on the basis of speech-quality judgments does not compromise speech recognition.
A speech test evaluation and presentation system is described. The test presentation subsystem has the flexibility and speed of live-voice testing while using recorded test materials. The speech test evaluation subsystem compares an individual subject's test performance on a monosyllabic word test with that of an average person with the same hearing loss. The elements needed to make such evaluations are discussed. Also, a trial of the procedure is described. The primary purpose of the trial was to obtain data that would provide a basis for statistical probability statements about individual monosyllabic word test results obtained in clinical settings. Data were collected from three audiology clinics in three different types of settings. Except for a few cases with highly asymmetric speech scores, all nonconductive hearing losses were included. Subject ages ranged from 8 to 92 years. Importance-weighted average pure-tone hearing losses ranged from 0.4 to 97.6 dB HL. Fifty-word recognition scores and audiograms for 2609 ears were included in the main analysis. Twenty-five-word recognition scores and audiograms for another 932 ears from one clinic were used in a subsidiary analysis. Results indicated that distributions of absolute speech recognition scores in hearing-impaired samples are highly skewed. However, after transformation of the scores into rationalized arcsine units (rau), the differences between individual subject scores and scores predicted from the audiogram were reasonably well described by the normal distribution. The standard deviation of this distribution of differences, for the data combined across the three audiology clinics, was approximately 13 rau.
A new procedure for fitting nonlinear hearing aids (National Acoustic Laboratories' nonlinear fitting procedure, version 1 [NAL-NL1]) is described. The rationale is to maximize speech intelligibility while constraining loudness to be normal or less. Speech intelligibility is predicted by the Speech Intelligibility Index (SII), which has been modified to account for the reduction in performance associated with increasing degrees of hearing loss, especially at high frequencies. Prescriptions are compared for the NAL-NL1, desired sensation level [input/output], FIG6, and a threshold version of the Independent Hearing Aid Fitting Forum procedures. For an average speech input level, the NAL-NL1 prescriptions are very similar to those of the well-established NAL-Revised, Profound procedure. Compared with the other procedures, NAL-NL1 prescribes less low-frequency gain for flat and upward sloping audiograms. It prescribes less high-frequency gain for steeply sloping high-frequency hearing losses. NAL-NL1 tends to prescribe less compression than the other procedures. All procedures differ considerably from one another for some audiograms.
Recent studies with adults have suggested that amplification at 4 kHz and above fails to improve speech recognition and may even degrade performance when high-frequency thresholds exceed 50-60 dB HL. This study examined the extent to which high frequencies can provide useful information for fricative perception for normal-hearing and hearing-impaired children and adults. Eighty subjects (20 per group) participated. Nonsense syllables containing the phonemes /s/, /f/, and /O/, produced by a male, female, and child talker, were low-pass filtered at 2, 3, 4, 5, 6, and 9 kHz. Frequency shaping was provided for the hearing-impaired subjects only. Results revealed significant differences in recognition between the four groups of subjects. Specifically, both groups of children performed more poorly than their adult counterparts at similar bandwidths. Likewise, both hearing-impaired groups performed more poorly than their normal-hearing counterparts. In addition, significant talker effects for /s/ were observed. For the male talker, optimum performance was reached at a bandwidth of approximately 4-5 kHz, whereas optimum performance for the female and child talkers did not occur until a bandwidth of 9 kHz.
This paper reports the aided and unaided speech-recognition scores from a group of 171 elderly hearing-aid wearers. All hearing-aid wearers were fit with identical instruments (linear Class-D amplifiers with output-limiting compression) and evaluated with a standard protocol. In addition to including multiple measures of speech recognition, an extensive set of physiological and perceptual measures of auditory function, as well as general measures of cognitive function, were completed prior to the hearing-aid fitting. Comparison of the results from this study to available norms suggested that this group of participants was fairly typical or representative for their hearing loss and age. Approaches to the prediction of general speech-recognition performance that were examined included methods based on an acoustical index, the Speech Intelligibility Index (SII), and others based on linear-regression statistical analysis. The latter approach proved to be the most successful, accounting for about two-thirds of the variance in speech-recognition performance, with the primary predictive factors being measures of hearing loss and cognitive function.
The purpose of the present study was to examine the benefits of providing audible speech to listeners with sensorineural hearing loss when the speech is presented in a background noise. Previous studies have shown that when listeners have a severe hearing loss in the higher frequencies, providing audible speech (in a quiet background) to these higher frequencies usually results in no improvement in speech recognition. In the present experiments, speech was presented in a background of multitalker babble to listeners with various severities of hearing loss. The signal was low-pass filtered at numerous cutoff frequencies and speech recognition was measured as additional high-frequency speech information was provided to the hearing-impaired listeners. It was found in all cases, regardless of hearing loss or frequency range, that providing audible speech resulted in an increase in recognition score. The change in recognition as the cutoff frequency was increased, along with the amount of audible speech information in each condition (articulation index), was used to calculate the "efficiency" of providing audible speech. Efficiencies were positive for all degrees of hearing loss. However, the gains in recognition were small, and the maximum score obtained by an listener was low, due to the noise background. An analysis of error patterns showed that due to the limited speech audibility in a noise background, even severely impaired listeners used additional speech audibility in the high frequencies to improve their perception of the "easier" features of speech including voicing.
We determined how the perceived naturalness of music and speech (male and female talkers) signals was affected by various forms of linear filtering, some of which were intended to mimic the spectral "distortions" introduced by transducers such as microphones, loudspeakers, and earphones. The filters introduced spectral tilts and ripples of various types, variations in upper and lower cutoff frequency, and combinations of these. All of the differently filtered signals (168 conditions) were intermixed in random order within one block of trials. Levels were adjusted to give approximately equal loudness in all conditions. Listeners were required to judge the perceptual quality (naturalness) of the filtered signals on a scale from 1 to 10. For spectral ripples, perceived quality decreased with increasing ripple density up to 0.2 ripple/ERB(N) and with increasing ripple depth. Spectral tilts also degraded quality, and the effects were similar for positive and negative tilts. Ripples and/or tilts degraded quality more when they extended over a wide frequency range (87-6981 Hz) than when they extended over subranges. Low- and mid-frequency ranges were roughly equally important for music, but the mid-range was most important for speech. For music, the highest quality was obtained for the broadband signal (55-16,854 Hz). Increasing the lower cutoff frequency from 55 Hz resulted in a clear degradation of quality. There was also a distinct degradation as the upper cutoff frequency was decreased from 16,845 Hz. For speech, there was a marked degradation when the lower cutoff frequency was increased from 123 to 208 Hz and when the upper cutoff frequency was decreased from 10,869 Hz. Typical telephone bandwidth (313 to 3547 Hz) gave very poor quality.
We previously described a model for loudness perception for people with cochlear hearing loss. However, that model is incompatible with our most recent and most satisfactory model of loudness for normal hearing. Here, we describe a loudness model that is applicable to both normal and impaired hearing. In contrast to our earlier model for impaired hearing, the new model correctly predicts: (1) that a sound at absolute threshold has a small but finite loudness; (2) that, for levels very close to the absolute threshold, the rate of growth of loudness is similar for normal ears and ears with cochlear hearing loss; (3) the relation between monaural and binaural threshold and loudness; (4) recent measures of equal-loudness contours. Like the earlier model, the new model can account for the loudness recruitment and reduced loudness summation that are typically associated with cochlear hearing loss.
The speech understanding of persons with "flat" hearing loss (HI) was compared to a normal-hearing (NH) control group to examine how hearing loss affects the contribution of speech information in various frequency regions. Speech understanding in noise was assessed at multiple low- and high-pass filter cutoff frequencies. Noise levels were chosen to ensure that the noise, rather than quiet thresholds, determined audibility. The performance of HI subjects was compared to a NH group listening at the same signal-to-noise ratio and a comparable presentation level. Although absolute speech scores for the HI group were reduced, performance improvements as the speech and noise bandwidth increased were comparable between groups. These data suggest that the presence of hearing loss results in a uniform, rather than frequency-specific, deficit in the contribution of speech information. Measures of auditory thresholds in noise and speech intelligibility index (SII) calculations were also performed. These data suggest that differences in performance between the HI and NH groups are due primarily to audibility differences between groups. Measures of auditory thresholds in noise showed the "effective masking spectrum" of the noise was greater for the HI than the NH subjects.
A discussion of the protocols used particularly in the clinical application of the Desired Sensation Level (DSL) Method is presented in this chapter. In the first section, the measurement and application of acoustic transforms is described in terms of their importance in the assessment phase of the amplification fitting process. Specifically, the implications of individual ear canal acoustics and their impact on accurately defining hearing thresholds are discussed. Detailed information about the statistical strength of the real-ear-to-coupler difference (RECD) measurement and how to obtain the measure in young infants is also provided. In addition, the findings of a study that examined the relationship between behavioral and electrophysiologic thresholds in real-ear SPL is described. The second section presents information related to the electroacoustic verification of hearing instruments. The RECD is discussed in relation to its application in simulated measurements of real-ear hearing instrument performance. In particular, the effects of the transducer and coupling method during the RECD measurement are described in terms of their impact on verification measures. The topics of insertion gain, test signals, and venting are also considered. The third section presents three summary tables that outline the hearing instrument fitting process for infants, children, and adults. Overall, this chapter provides both clinical and scientific information about procedures used in the assessment and verification stages of the DSL Method.
The Desired Sensation Level (DSL) Method was revised to support hearing instrument fitting for infants, young children, and adults who use modern hearing instrument technologies, including multichannel compression, expansion, and multimemory capability. The aims of this revision are to maintain aspects of the previous versions of the DSL Method that have been supported by research, while extending the method to account for adult-child differences in preference and listening requirements. The goals of this version (5.0) include avoiding loudness discomfort, selecting a frequency response that meets audibility requirements, choosing compression characteristics that appropriately match technology to the user's needs, and accommodating the overall prescription to meet individual needs for use in various listening environments. This review summarizes the status of research on the use of the DSL Method with pediatric and adult populations and presents a series of revisions that have been made during the generation of DSL v5.0. This article concludes with case examples that illustrate key differences between the DSL v4.1 and DSL v5.0 prescriptions.
In a laboratory study, we found that normal-hearing and hearing-impaired listeners preferred less than normal overall calculated loudness (according to a loudness model of Moore & Glasberg, 1997). The current study verified those results using a research hearing aid. Fifteen hearing-impaired and eight normal-hearing participants used the hearing aid in the field and adjusted a volume control to give preferred loudness. The hearing aid logged the preferred volume control setting and the calculated loudness at that setting. The hearing-impaired participants preferred, in median, loudness levels of -14 phon re normal for input levels from 50 to 89 dB SPL. The normal-hearing participants preferred close to normal overall loudness. In subsequent laboratory tests, using the same hearing aid, both hearing-impaired and normal-hearing listeners preferred less than normal overall calculated loudness, and larger reductions for higher input levels In summary, the hearing-impaired listeners preferred less than normal overall calculated loudness, whereas the results for the normal-hearing listeners were inconclusive.
This study questions the basic assumption that prescriptive methods for nonlinear, wide dynamic range compression (WDRC) hearing aids should restore overall loudness to normal. Fifteen normal-hearing listeners and twenty-four hearing-impaired listeners (with mild to moderate hearing loss, twelve with and twelve without hearing aid experience) participated in laboratory tests. The participants first watched and listened to video sequences and rated how loud and how interesting the situations were. For the hearing-impaired participants, gain was applied according to the NAL-NL1 prescription. Despite the fact that the NAL-NL1 prescription led to less than normal overall calculated loudness, according to the loudness model of Moore and Glasberg (1997), the hearing-impaired participants rated loudness higher than the normal-hearing participants. The participants then adjusted a volume control to preferred overall loudness. Both normal-hearing and hearing-impaired participants preferred less than normal overall calculated loudness. The results from the two groups of hearing-impaired listeners did not differ significantly.