[Show abstract][Hide abstract] ABSTRACT: Given the interest in comparing speech production development in children with normal hearing and hearing impairment, it is important to evaluate how variables within speech elicitation tasks can differentially affect the acoustics of speech production for these groups. In a first experiment, children (6-14 years old) with cochlear implants produced a set of monosyllabic words either in isolation or while simultaneously signing the word. Acoustical analyses indicated no change in word duration, voice onset time, intensity, or fundamental frequency between isolated and simultaneous signing conditions. In a second experiment, the same children verbally repeated words that were signed by a video model. The model either signed with inflection or without. Words repeated after inflected models were higher in fundamental frequency and intensity and were more intelligible. In addition, children with poorer speech perception skills sometimes produced the monosyllables as 2 syllables, but this only occurred for words that had multiple sign movements. The results have implications for the comparison of speech development between children with normal hearing and those with hearing impairment.
Journal of Speech Language and Hearing Research 03/2007; 50(1):83-96. DOI:10.1044/1092-4388(2007/007) · 2.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this investigation was to examine the nature and frequency of deviant speech and voice physiology in children who are hard of hearing (HH).
Ten HH children (age, 5 to 15 yrs) participated. Their hearing losses ranged in severity from moderate to severe. The following speech/voice physiological measures were examined: frequency of occurrence of negative intraoral air pressure (-Po), magnitude of Po, phonatory air flow, nasal air flow, voice onset time (VOT), and fundamental frequency (F0). Findings were compared with data previously collected from 56 children with normal hearing and 7 children with cochlear implants (Higgins, McCleary, Carney, & Schulte, 2003).
Five of the 10 HH children exhibited deviant speech/voice behaviors. Only one showed deviancy on more than one measure. In addition, 8 HH children had some borderline-deviant speech behavior. The frequency and degree of speech/voice deviancy for the children in the present study was far less than what we previously had observed for children who underwent cochlear implantation after 5 yrs of age (Higgins et al., 2003). This was the case even for a child with a cochlear implant from our earlier study who eventually achieved speech perception scores that were as good as or better than some of the HH children in the present investigation.
Deviant speech/voice physiology occurs to a limited extent for some HH children. Of the measures that we examined, those related to vocal fold tension and vocal fold articulation appeared to be most sensitive to the effects of diminished auditory input and feedback that occurs for HH children. Data from this and other studies suggest that abnormally high F0 occurs for about 20% of HH children and may be associated with poor speech perception skills. Future studies should examine whether earlier implantation can help deaf children to produce speech that is at least as normal as that of HH children.
Ear and Hearing 01/2006; 26(6):546-58. DOI:10.1097/01.aud.0000188151.99086.a3 · 2.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: It is common among clinicians to ask children to produce their best speech during intervention. However, it is unclear whether children know how to respond to these directions and whether any contingent changes in their production actually result in better speech. Normal and best speech for children with normal hearing (NH) and cochlear implants (CI) were compared on a variety of acoustic measures. The children (7 to 14 years of age) were asked to read ten simple sentences to train up a fictional automatic speech recognizer for children. They subsequently produced the same sentences with their best and then very best, very clearest speech (ostensibly to test the recognizer). Sentence, pause, and vowel duration were calculated for all sentences as well as vowel intensity and fundamental frequency. Additionally, phonetic distinctiveness was evaluated through vowel space size and voice onset time differences between voiced and voiceless stops. NH children demonstrated patterns of best speech that resemble adult clear speech productions. CI children’s speech resembled NH best speech in all elicitation conditions, except that they slowed (their already slower) speaking rate for best speech. The results indicate that clear speech can be produced by children. [Work supported by NIH.]
The Journal of the Acoustical Society of America 01/2006; 119(5):3341. DOI:10.1121/1.4786439 · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Studies of clear versus conversational speech have shown perceptual and acoustic differences. The basic premise is that the speaker understands the direction to speak more clearly, and translates the direction to speech motor acts. Children with hearing losses receive intervention during which they are instructed to use their best speech. The purpose of this study was to determine: (1) whether hearing-impaired children's intelligibility changed with directions to use better speech, and (2) whether these children's speech was judged to be clearer when they had intended to produce clear speech. There were two groups of speakers: 14 deaf children with cochlear implants and 7 hard-of-hearing children with hearing aids. Each produced ten short sentences using typical speech, better speech, and best speech. All sentences were presented to a total of 189 adult listeners with normal hearing who wrote down what they heard. Hard-of-hearing children had average speech intelligibility of 98% those with implants averaged 66%. Both groups had very small increases across conditions. All sentences in three speech conditions were presented in a paired-comparison task to ten additional listeners. Results of clarity judgments will be discussed in relation to the relatively small changes in speech intelligibility. [Research supported by NIH.]
The Journal of the Acoustical Society of America 01/2005; 118:1962-1962. DOI:10.1121/1.4781542 · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purposes of this investigation were 1) to describe speech/voice physiological characteristics of prelingually deafened children before and after cochlear implantation and determine whether they fall into a range that would be considered deviant, 2) to determine whether selected deviant articulatory and phonatory behaviors of children with cochlear implants persist despite long-term cochlear implant use and continued participation in aural rehabilitation services, and 3) to determine whether further development of deviant articulatory and phonatory behaviors occurs postimplantation.
Seven prelingually deafened children who received cochlear implants after 5 yr of age were followed from shortly before implantation until 5 to 6 yr postimplantation. These children received their early education in a Total Communication environment and used the Nucleus 22-electrode cochlear implant. All of them initially used the MPEAK speech processing strategy, and five of them eventually upgraded to the SPEAK speech processing strategy. Speech/voice physiological measurements that were obtained periodically from the children included intraoral air pressure (P(o)), nasal and phonatory air flow, voice onset time (VOT), and fundamental frequency (F(o)). Data from the deaf children were compared with a database from 56 children with normal hearing to determine when the deaf children exhibited "deviant" speech/voice behaviors. Speech/voice behaviors were considered "deviant" if they never occurred for children with normal hearing or were associated with z-scores that were outside the range of +/-2.0.
The deaf children showed a wide range of deviant speech and voice behaviors both pre- and post-cochlear implant. The most frequently occurring atypical behaviors were use of negative P(o), high P(o) for [b, m], long and short VOT for [p], and high F(o). Some deviant behaviors improved post-cochlear implant. However, deviant behaviors often persisted for several years post-cochlear implant. There was considerable evidence of further development of deviant behaviors post-cochlear implant. All of the deaf children demonstrated deviancy on at least two of our measures at the last data collection interval (5 to 6 yr post-cochlear implant).
Children who received cochlear implants after 5 yr of age and who were educated in a Total Communication setting showed persistence and further development of deviant speech/voice behaviors for several years post-cochlear implant. Although our findings cannot be generalized to other populations of children with cochlear implants (i.e., those who were implanted earlier, those educated in auditory-oral programs), it seems wisest at the present time not to assume that children's deviant speech/voice behaviors will remit spontaneously with continued cochlear implant use. Our data provide an important comparative database for future investigations of pediatric cochlear implant users who have had shorter periods of auditory deprivation and who have received cochlear implants with more current technological features. Longitudinal Changes in Children's Speech and Voice Physiology after Cochlear Implantation
Ear and Hearing 03/2003; 24(1):48-70. DOI:10.1097/01.AUD.0000051846.71105.AF · 2.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: EGGW is a phonatory parameter that can be derived from electroglottographic (EGG) signals and used to infer the relative degree of vocal fold contact. Vocal fold models predict that men will exhibit medial bulging of their vocal folds during phonation but women will not. These models lead us to expect gender differences in the magnitude of EGGW. Nevertheless, significant gender differences in EGGW for adults with normal voices have not been documented in previous studies when EGGW was computed from criterion lines placed at 25%-40% of the amplitude of the uninverted EGG wave form. We hypothesized that EGGW would better reflect gender differences in vocal fold adductory patterns if EGGW was computed from portions of the wave form that were associated with more vocal fold contact. EGGW was measured for seven men and seven women with normal voices. When EGGW was computed from segments of the wave form that were associated with relatively greater vocal fold contact (i.e., using criterion levels of > or = 55%), findings were consistent with the gender-specific adductory patterns that have been proposed from vocal fold models. Guidelines for appropriate placement of criterion lines when computing EGGW are discussed.
The Journal of the Acoustical Society of America 05/2002; 111(4):1865-71. DOI:10.1121/1.1456517 · 1.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this investigation was to determine how suddenly diminished auditory feedback affects articulatory behaviors for prelingually deafened children with cochlear implants (CIs).
Two 6-yr-old children served as participants. Considering their level of hearing impairment, one child had above average speech perception and production skills while the other child had exceptionally good speech perception and production abilities. Baseline data were collected four times over the course of 2 days with the children wearing their CIs. For three additional days, data were collected while the children wore their CIs (ON condition) and then again after their CIs had been deactivated for 1 hr (OFF condition). Variables assessed included amount of jaw opening, F1, F2, nasal air flow, voice onset time (VOT), voicing duration, and the magnitude and duration of intraoral air pressure (Po). Findings were related to each other and to previously reported phonatory findings from the same two children (Higgins, McCleary, & Schulte, 1999) to determine whether changes in articulatory variables in the OFF condition were consistent with a direct effect of diminished auditory feedback or an indirect influence of suprasegmental parameters.
Both children exhibited consistent and significant changes in articulatory parameters in the absence of auditory feedback. Such changes occurred more often for the child who had especially proficient speech perception and production skills. Some changes (i.e., reduced Po for [p] and reduced nasal air flow for [m]) appeared related to the influence of suprasegmental parameters, in particular, reduced subglottal air pressure. Other effects (i.e., increased F2 for [a] and reduced VOT for [p]) were suggestive of changes in the children's abilities to maintain appropriate articulatory placements and timing. Finally, a few changes (reduced jaw opening for [i] and increased Po duration for [p]) may have reflected compensatory strategies to maintain correct tongue placement and enhance temporal distinctions in the absence of auditory feedback.
Based on the data of our two participants, it appears that some prelingually deafened children with CIs and good speech perception/production skills rely on auditory feedback to maintain articulatory precision. In the absence of auditory feedback, such children may demonstrate changes in articulatory placement and timing. In addition, data from one of our participants are consistent with the idea that some children may be aware that their articulatory control is compromised in the absence of auditory feedback and attempt to compensate by altering articulatory durations or the range of associated articulatory movements.
Ear and Hearing 03/2001; 22(1):29-45. DOI:10.1097/00003446-200102000-00004 · 2.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The primary purpose of this study was to determine if negative intraoral air pressures (-Po) produced by young deaf children can be treated effectively with visual feedback. We used two forms of visual feedback. One was a display of the Po signal on an oscilloscope, and the other was movement of cellophane streamers placed in front of the children's mouths. Participants were two 5-year-old boys who had been using cochlear implants (CIs) for less than 6 months. Both children were congenitally deafened and had very limited speech production and perception skills. In addition to frequent usage of -Po, both children exhibited deviant phonatory behaviors, so phonatory goals were incorporated into treatment. The magnitude and direction of Po was monitored, as well as fundamental frequency and electroglottograph cycle width. Data were collected at baseline, before and after treatment sessions, and 7 weeks after termination of treatment. One child responded well to treatment of -Po with both forms of visual feedback, and progress was maintained at follow-up. For the other child, +Po occurred more frequently as the study progressed, and he rarely produced -Po by the end of the investigation. However, because changes were evident in baseline as well as during treatment, it is difficult to attribute his more frequent use of +Po specifically to treatment. The phonation of the two children changed in ways that were consistent with their phonatory goals, although the degree of change was not always significant. Change was more evident for phonatory behaviors that could be shaped with visual feedback. Although both children exhibited some undesirable speech/voice behaviors in response to visual feedback, there was no evidence of long-lasting mislearning. Although our data are limited, it appears that treatment of -Po can be efficacious for some young children with Cls, even those with very poor speech perception and speech production skills. Further, treatment of -Po can be incorporated effectively with other speech production goals.
American Journal of Speech-Language Pathology 02/2000; 9(1):21. DOI:10.1044/1058-0360.0901.21 · 1.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purposes of this investigation were 1) to determine whether short-term auditory deprivation results in systematic phonatory changes for prelingually deafened children who use cochlear implants (CIs) and 2) to determine whether such changes are similar to those that have been reported for postlingually deafened adults.
Participants were two 6-yr-old children with CIs. Both children had been prelingually deafened, had good to excellent speech production and speech perception skills, and had been using their CIs for 2.5 yr. A single-subject design was used. Intraoral air pressure (Po), phonatory air flow (Vl), electroglottograph (EGG) cycle width, fundamental frequency (F0), and intensity were measured during syllable production over two baseline days and three experimental days. Data were collected twice on each baseline day while the children wore their CIs, with a 1 hr break between data collection sessions. On experimental days, data were collected while the children wore their CIs (ON condition) and after their CIs had been removed for 1 hr (OFF condition).
Both children demonstrated highly variable phonatory behaviors in baseline. The child with the more proficient speech production and perception skills showed consistent and significant reductions in Po, F0, and intensity in the OFF condition. These findings were dissimilar to those that occurred with repeated testing in the baseline condition and so were attributed to the sudden loss of auditory feedback. The other child showed a consistent and significant increase in mean Vl in the OFF condition. However, this child exhibited a similar finding with repeated testing in the baseline condition. Therefore, increased Vl in the OFF condition may have represented a practice effect. She also showed a small and consistent decrease in F0 in the OFF condition when F0 was derived from acoustic data, but this effect was not reliable in another data set when F0 was derived from the EGG signal. Our results with prelingually deafened children were inconsistent with reports of increased intensity and F0 in the absence of auditory feedback for postlingually deafened adults with CIs.
Some prelingually deafened children who are successful CI users appear to use auditory feedback to self-monitor phonation. We suggest that the participant in our investigation who showed systematic phonatory changes in response to diminished auditory feedback was using auditory feedback primarily to stabilize her phonatory behaviors. She may not have had adequate experience with auditory feedback or adequate flexibility in her use of feedback mechanisms to implement the phonatory compensations that late-deafened adults use when auditory feedback suddenly is diminished. We further suggest that the phonatory changes that she exhibited during short-term auditory deprivation reflected disruption of her typical speaking strategies or apprehension about speaking when her ability to self-monitor auditorily was compromised.
Ear and Hearing 11/1999; 20(5):426-38. DOI:10.1097/00003446-199910000-00006 · 2.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to determine if phonatory air flow characteristics differed among women with adductor spasmodic dysphonia (AdSD), muscle tension dysphonia (MTD), and normal phonation. Phonatory air flow signals were gathered during [pa] syllable repetitions. Mean phonatory air flow, coefficients of variation, and the presence of large air flow perturbations (75 ml/s or more) were examined for the three groups of speakers. There was no significant difference in mean phonatory air flow across groups, and very large intersubject variation in mean phonatory air flow occurred for both the AdSD and MTD groups. Coefficients of variation were similar for the groups of women with MTD and normal phonation but were significantly larger for the group with AdSD. Air flow perturbations were common with AdSD and rare with MTD. Relatively large coefficients of variation and air flow perturbations of at least 75 ml/s did occur for some women with normal voices who were 70 years of age or older. It appears that intrasubject variability in phonatory air flow may aid in the differentiation of AdSD and MTD when used in conjunction with other elements of a thorough voice evaluation. However, the potential contribution of aging to increased intrasubject variability in phonatory air flow must be considered when interpreting findings.
Journal of Speech Language and Hearing Research 03/1999; 42(1):101-11. DOI:10.1044/jslhr.4201.101 · 2.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this investigation was to study the interaction between the supralaryngeal and laryngeal components of the speech mechanism by examining vowel-related effects for a variety of vocal fold articulatory and phonatory measures. Secondary issues were to determine if vowel-related differences were influenced by the nature of the speaking task or gender. Between-vowel differences in estimated subglottal air pressure, peak oral air flow, mean phonatory air flow, air flow near the termination of the vowel, electroglottograph cycle width (EGGW), fundamental frequency, and voice onset time were examined for men and women during syllable repetitions and sentence productions. Significant vowel-related differences were found for all of the measures except mean phonatory air flow, and generally were not influenced by speaking task or gender. Vowel-related effects for estimated subglottal air pressure, peak oral air flow, fundamental frequency, and VOT were consistent with some earlier studies. New findings included vowel-related differences in EGGW and air flow near the termination of the vowel. We propose a model that includes the contribution of mechanical forces, reflexive neural activity, and learned neural activity to explain vowel-related effects. When vowel height is varied, changes in laryngeal cartilage positioning and vocal fold and vocal tract tension appear to influence laryngeal articulatory and phonatory function.
Journal of Speech Language and Hearing Research 09/1998; 41(4):712-24. DOI:10.1044/jslhr.4104.712 · 2.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The primary purpose of this investigation was to examine deaf children's use of negative intraoral air pressures (-Po's) from a physiological and a phonological perspective, with the hope of gathering insight into the strategies these children use to produce speech. A secondary purpose was to compare the effectiveness of two methods of treating these deviant productions. Subjects were four profoundly deaf children, age 6:6-9:2, who used cochlear implants and had demonstrated persistent use of -Po's. Po's were collected during production of CV syllables with initial [p] and [b] and a variety of vowel contexts. Two of the children used -PO's more often before low than high vowels. We suggest that this vowel-based pattern may result when deaf children learn to lower their larynges in response to visible jaw lowering cues. Another child presented with a pattern of more frequent -Po's before front than back vowels, suggesting that she may have expanded her pharynx anteriorly as she attempted to achieve an anterior tongue placement. Two children also clearly used -Po's more frequently for voiced than voiceless stops, possibly resulting from a tendency to use the degree rather than the timing of vocal fold adduction to distinguish voiceless and voiced phonemes. Two of the children were enrolled in a single-subject multiple baseline study to compare the effectiveness of traditional articulation treatment and visual-feedback treatment. The child who was a far less proficient talker demonstrated rapid and sustained change, whereas the better talker demonstrated minimal change with treatment. This study provides evidence that (a) deaf children use speech production strategies quite unlike those of normally hearing children and (b) deviant speech behaviors of deaf children should be treated before they become part of functional phonological systems. This work highlights the need to consider the unique speech behaviors of deaf children, and their reliance on alternate feedback mechanisms, when developing assessment and treatment procedures.
Journal of speech and hearing research 11/1996; 39(5):957-67.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this investigation was to study the impact of hearing loss on phonatory, velopharyngeal, and articulatory functioning using a comprehensive physiological approach. Electroglottograph (EGG), nasal/oral air flow, and intraoral air pressure signals were recorded simultaneously from adults with impaired and normal hearing as they produced syllables and words of varying physiological difficulty. The individuals with moderate-to-profound hearing loss had good to excellent oral communication skills. Intraoral pressure, nasal air flow, durations of lip, velum, and vocal fold articulations, estimated subglottal pressure, mean phonatory air flow, fundamental frequency, and EGG abduction quotient were compared between the two subject groups. Data from the subjects with hearing loss also were compared across aided and unaided conditions to investigate the influence of auditory feedback on speech motor control. The speakers with hearing loss had significantly higher intraoral pressures, subglottal pressures, laryngeal resistances, and fundamental frequencies than those with normal hearing. There was notable between-subject variability. All of the individuals with profound hearing loss had at least one speech/voice physiology measure that fell outside of the normal range, and most of the subjects demonstrated unique clusters of abnormal behaviors. Abnormal behaviors were more evident in the phonatory than articulatory or velopharyngeal systems and were generally consistent with vocal fold hyperconstriction. There was evidence from individual data that vocal fold posturing influenced articulatory timing. The results did not support the idea that the speech production skills of adults with moderate-to-profound hearing loss who are good oral communicators deteriorate when there are increased motoric demands on the velopharyngeal and phonatory mechanism. Although no significant differences were found between the aided and unaided conditions, 7 of 10 subjects showed the same direction of change for subglottal pressure, intraoral pressure, nasal air flow, and the duration of lip and vocal fold articulations. We conclude that physiological assessments provide important information about the speech/voice production abilities of individuals with moderate-to-profound hearing loss and are a valuable addition to standard assessment batteries.
Journal of speech and hearing research 07/1994; 37(3):510-21. DOI:10.1044/jshr.3703.510
[Show abstract][Hide abstract] ABSTRACT: The purpose of this investigation was to quantify the normal intrasubject performance variability of four measures of phonatory function within and across sessions. Two different speaking tasks, syllable series and sentence production, were used to determine if more natural speaking tasks resulted in greater intrasubject variability. Vowel type ([i] versus [a]) also was varied. Estimated subglottal air pressure, mean phonatory air flow, abduction quotient, and fundamental frequency were derived from aerodynamic and electroglottographic signals obtained from 11 normally speaking men and 10 normally speaking women on four different days. Relative intrasubject variability was compared across speaking task, gender, and vowel type. Average across-session intrasubject variability was 5% for fundamental frequency and abduction quotient, 8% for estimated subglottal air pressure, and 15% for mean phonatory air flow during syllable repetition. There was significantly greater intrasubject variability for mean phonatory air flow and abduction quotient for the sentence repetition task. There were no significant differences in intrasubject variability across gender and vowel type. The data were used to compute cutoff values that represent the amount of variability that would be considered within normal limits. These normal data can be used for comparison when assessing and monitoring the phonatory abilities of individuals with voice disorders.
Journal of speech and hearing research 03/1994; 37(1):38-45.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this investigation was to compare the effects of two speaking tasks on laryngeal measures obtained from inverse-filtered air flow and electroglottograph (EGG) waveforms. Flow amplitude, air flow duty cycle, EGG duty cycle, and fundamental frequency were measured for normal young and aged adults during vowel prolongation and syllable repetition. There were significant between-task differences for flow amplitude and fundamental frequency. Variability appeared no greater for syllable repetition than vowel prolongations. Syllable repetition was slightly better than vowel prolongation for differentiating the vocal behaviors of aged and young speakers. Between-task relationships were strong for fundamental frequency and more moderate for the other laryngeal measures. It was concluded that syllable repetition would be preferable to vowel prolongation for measurement of aerodynamic and EGG parameters and that findings could be generalized across speaking tasks for fundamental frequency but not air flow and duty cycle measures.
Journal of Voice 04/1993; 7(1):47-53. DOI:10.1016/S0892-1997(05)80111-0 · 1.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Selected phonatory behaviors of healthy aged and young men and women were compared. Inverse-filtered air flow, electroglottograph (EGG), and intraoral air pressure signals were recorded as subjects phonated in each of four conditions: normal, soft, loud, loud/high pitched. Minimum flow offset, flow amplitude, air flow duty cycle, EGG duty cycle, estimated subglottal pressure, and fundamental frequency were derived from the recorded signals and compared among age/gender groups. Males had significantly greater flow amplitude than females regardless of age. Significant Age x Sex interactions were found for fundamental frequency and duty cycle measures. Duty cycles and fundamental frequency increased for males and decreased for females with aging. For the normal phonatory condition, aged men had significantly greater duty cycle measures, flow amplitude, and estimated subglottal pressure than young men. There were significant differences in fundamental frequency and EGG duty cycle between aged and young women during normal phonation. It was concluded that the effects of aging on phonatory behaviors are different in degree and kind for men and women. Fewer significant age-related differences in phonatory measures for women than men were consistent with reports of less age-related laryngeal degeneration in females than males.
Journal of speech and hearing research 11/1991; 34(5):1000-10. DOI:10.1044/jshr.3405.1000
[Show abstract][Hide abstract] ABSTRACT: The bandwidths for summation at threshold were measured for subjects with normal hearing and subjects with sensorineural hearing loss. Thresholds in quiet and in the presence of a masking noise were measured for complex stimuli consisting of 1 to 40 pure-tone components spaced 20 Hz apart. The single component condition consisted of a single pure tone at 1100 Hz; additional components were added below this frequency, in a replication of the Gässler [Acustica 4, 408-414 (1954)] procedure. For the normal subjects, thresholds increased approximately 3 dB per doubling of bandwidth for signal bandwidths exceeding the critical bandwidth. This slope was less for the hearing-impaired subjects. Summation bandwidths, as estimated from two-line fits, were wider for the hearing-impaired than for the normal subjects. These findings provide evidence that hearing-impaired subjects integrate sound energy over a wider-than-normal frequency range for the detection of complex signals. A second experiment used stimuli similar to those of Spiegel [J. Acoust. Soc. Am. 66, 1356-1363 (1979)], and added components both above and below the frequency of the initial component. Using these stimuli, the slope of the threshold increase beyond the critical bandwidth was approximately 1.5 dB per doubling of bandwidth, thus replicating the Spiegel (1979) experiment. It is concluded that the differences between the Gässler (1954) and Spiegel (1979) studies were due to the different frequency content of the stimuli used in each study. Based upon the present results, it would appear that the slope of threshold increase is dependent upon the direction of signal expansion, and the size of the critical bands into which the signal is expanded.
The Journal of the Acoustical Society of America 01/1991; 88(6):2625-30. DOI:10.1121/1.399982 · 1.50 Impact Factor