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ABSTRACT: The perception of modulation of a tone interrupted by a noise burst was investigated. The tone and its modulation were perceived as continuing through the noise. In experiment 1, subjects rated the similarity of an uninterrupted tone and a tone interrupted by noise, in terms of the perceived level and modulation depth of the sinusoidal carrier. The values of these parameters in the central portion of the uninterrupted tone were systematically varied. Both amplitude and frequency modulation (AM and FM) were used. The results indicated that the perceived level and modulation depth of the carrier did not change greatly during the noise burst. When the modulation rate differed before and after the noise burst, the modulation-rate transition was perceived to occur near the end of the noise burst for the FM stimuli. Hence, for these stimuli, the continuity illusion appears to be dominated by the portion of the tone before, rather than after, the interruption. Results for the AM stimuli showed a non-significant trend in the same direction. Experiment 2 used forced-choice tasks to evaluate the ability to detect a change in the ongoing phase of AM and FM following interruption by a noise burst. The results confirmed earlier findings for FM tones, and extended them to AM tones, showing that listeners lost track of the phase of the modulation, even though the modulation was perceived as continuous.
Hearing Research 01/2006; 210(1-2):30-41. · 2.70 Impact Factor
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ABSTRACT: Vowels are mainly classified by the positions of peaks in their frequency spectra, the formants. For normal-hearing subjects, change detection and direction discrimination were measured for linear glides in the center frequency (CF) of formantlike sounds. A CF rove was used to prevent subjects from using either the start or end points of the glides as cues. In addition, change detection and starting-phase (start-direction) discrimination were measured for similar stimuli with a sinusoidal 5-Hz formant-frequency modulation. The stimuli consisted of single formants generated using a number of different stimulus parameters including fundamental frequency, spectral slope, frequency region, and position of the formant relative to the harmonic spectrum. The change detection thresholds were in good agreement with the predictions of a model which analyzed and combined the effects of place-of-excitation and temporal cues. For most stimuli, thresholds were approximately equal for change detection and start-direction discrimination. Exceptions were found for stimuli that consisted of only one or two harmonics. In a separate experiment, it was shown that change detection and start-direction discrimination of linear and sinusoidal formant-frequency modulations were impaired by off-frequency frequency-modulated interferers. This frequency modulation detection interference was larger for formants with shallow than for those with steep spectral slopes.
The Journal of the Acoustical Society of America 06/2005; 117(5):3042-53. · 1.55 Impact Factor
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ABSTRACT: Experiment 1 measured pure-tone frequency difference limens (DLs) at 1 and 4 kHz. The stimuli had two steady-state portions, which differed in frequency for the target. These portions were separated by a middle section of varying length, which consisted of a silent gap, a frequency glide, or a noise burst (conditions: gap, glide, and noise, respectively). The noise burst created an illusion of the tone continuing through the gap. In the first condition, the stimuli had an overall duration of 500 ms. In the second condition, stimuli had a fixed 50-ms middle section, and the overall duration was varied. DLs were lower for the glide than for the gap condition, consistent with the idea that the auditory system contains a mechanism specific for the detection of dynamic changes. DLs were generally lower for the noise than for the gap condition, suggesting that this mechanism extracts information from an illusory glide. In a second experiment, pure-tone frequency direction-discrimination thresholds were measured using similar stimuli as for the first experiment. For this task, the type of the middle section hardly affected the thresholds, suggesting that the frequency-change detection mechanism does not facilitate the identification of the direction of frequency changes.
The Journal of the Acoustical Society of America 08/2004; 116(1):491-501. · 1.55 Impact Factor
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Cortex 01/2002; 37(5):706-9. · 6.08 Impact Factor
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ABSTRACT: The influence of hearing loss and aging on the perceptual organization of sound sequences was investigated by comparing the ability of young normal-hearing subjects and elderly subjects having either impaired or normal hearing for their age to form perceptual auditory streams from sequences of harmonic complex tones as a function of differences in fundamental frequency (F0). The sequences consisted of repeating triplets of harmonic complex tones separated by a silence (ABA-). In conditions in which the F0s of the A and B tone were so low that the harmonics could not be individually resolved by the peripheral auditory system even in the young normal-hearing subjects, those subjects showed similar stream segregation performance to the elderly hearing-impaired subjects. In contrast, when the F0s of the tones were high enough for the harmonics to be largely resolved at the auditory periphery in normal-hearing subjects, but presumably unresolved in the elderly subjects, the former showed significantly more stream segregation than the latter. These results, which cannot be consistently explained in terms of age differences, suggest that auditory stream segregation is adversely affected by reduced peripheral frequency selectivity of elderly individuals. This finding has implications for the understanding of the listening difficulties experienced by elderly individuals in cocktail-party situations.
British Journal of Audiology 07/2001; 35(3):173-82.
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ABSTRACT: Two pairs of experiments studied the effects of attention and of unilateral neglect on auditory streaming. The first pair showed that the build up of auditory streaming in normal participants is greatly reduced or absent when they attend to a competing task in the contralateral ear. It was concluded that the effective build up of streaming depends on attention. The second pair showed that patients with an attentional deficit toward the left side of space (unilateral neglect) show less stream segregation of tone sequences presented to their left than to their right ears. Streaming in their right ears was similar to that for stimuli presented to either ear of healthy and of brain-damaged controls, who showed no across-ear asymmetry. This result is consistent with an effect of attention on streaming, constrains the neural sites involved, and reveals a qualitative difference between the perception of left- and right-sided sounds by neglect patients.
Journal of Experimental Psychology Human Perception & Performance 03/2001; 27(1):115-27. · 3.06 Impact Factor
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ABSTRACT: Two experiments examined the relationship between temporal pitch (and, more generally, rate) perception and auditory lateralization. Both used dichotic pulse trains that were filtered into the same high (3,900-5,400-Hz) frequency region in order to eliminate place-of-excitation cues. In experiment 1, a 1-s periodic pulse train of rate Fr was presented to one ear, and a pulse train of rate 2Fr was presented to the other. In the "synchronous" condition, every other pulse in the 2Fr train was simultaneous with a pulse in the opposite ear. In each trial, subjects concentrated on one of the two binaural images produced by this mixture: they matched its perceived location by adjusting the interaural level difference (ILD) of a bandpass noise, and its rate/pitch was then matched by adjusting the rate of a regular pulse train. The results showed that at low Fr (e.g., 2 Hz), subjects heard two pulse trains of rate Fr, one in the "higher rate" ear, and one in the middle of the head. At higher Fr (>25 Hz) subjects heard two pulse trains on opposite sides of the midline, with the image on the higher rate side having a higher pitch than that on the "lower rate" side. The results were compared to those in a control condition, in which the pulses in the two ears were asynchronous. This comparison revealed a duplex region at Fr > 25 Hz, where across-ear synchrony still affected the perceived locations of the pulse trains, but did not affect their pitches. Experiment 2 used a 1.4-s 200-Hz dichotic pulse train, whose first 0.7 s contained a constant interaural time difference (ITD), after which the sign of the ITD alternated between subsequent pulses. Subjects matched the location and then the pitch of the "new" sound that started halfway through the pulse train. The matched location became more lateralized with increasing ITD, but subjects always matched a pitch near 200 Hz, even though the rate of pulses sharing the new ITD was only 100 Hz. It is concluded from both experiments that temporal pitch perception is not driven by the output of binaural mechanisms.
The Journal of the Acoustical Society of America 03/2001; 109(2):686-700. · 1.55 Impact Factor
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ABSTRACT: The mechanism(s) determining pitch may assign less weight to portions of a sound where the frequency is changing rapidly. The present experiments explored the possible effect of this on the overall pitch of frequency-modulated sounds. Pitch matches were obtained between an adjustable unmodulated sinusoid and a sinusoidal carrier that was frequency modulated using a highly asymmetric function with the form of a repeating U or inverted U shaped function. The amplitude was constant during the 400-ms presentation time of each stimulus, except for 10-ms raised-cosine onset and offset ramps. In experiment 1, the carrier level was 50 dB SPL and the geometric mean of the instantaneous frequency of the modulated carrier, fc, was either 0.5, 1, 2, or 8 kHz. The modulation rate (fm) was 5, 10, or 20 Hz. The overall depth (maximum to minimum) of the FM was 8% of fc. For all carrier frequencies, the matched frequency was shifted away from the mean carrier frequency, downwards for the U shaped function stimuli and upwards for the repeated inverted U shaped function stimuli. The shift was typically slightly greater than 1% of fc, and did not vary markedly with fc. The effect of fm was small, but there was a trend for the shifts to decrease with increasing fm for fc = 0.5 kHz and to increase with increasing fm for fc = 2 kHz. In experiment 2, the carrier level was reduced to 20 dB SL and matches were obtained only for fc = 2 kHz. Shifts in matched frequency of about 1% were still observed, but the trend for the shifts to increase with increasing fm no longer occurred. In experiment 3, matches were obtained for a 4-kHz carrier at 50 dB SPL. Shifts of about 1% again occurred, which did not vary markedly with fm. The shifts in matched frequency observed in all three experiments are not predicted by models based on the amplitude- or intensity-weighted average of instantaneous frequency (EWAIF or IWAIF). The shifts (and the pitch shifts observed earlier for two-tone complexes and for stimuli with simultaneous AM and FM) are consistent with a model based on the assumption that the overall pitch of a frequency-modulated sound is determined from a weighted average of period estimates, with the weight attached to a given estimate being inversely related to the short-term rate of change of period and directly related to a compressive function of the amplitude.
The Journal of the Acoustical Society of America 03/2001; 109(2):701-12. · 1.55 Impact Factor
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ABSTRACT: Unilateral neglect is frequently characterized by the presence of extinction, which is a lack of awareness to contralesional visual stimuli in the presence of those further towards the ipsilesional side. It has been established that this visual extinction can be reduced if the stimuli are grouped together into a single object. However, attention between and within auditory objects has never before been studied. We demonstrate for the first time that unilateral neglect--hitherto thought primarily to be a disorder of visuospatial processing-- involves a specific deficit in allocating attention between auditory objects separated only in time and not in space. Importantly, this deficit is restricted to comparisons between sounds: the patients' ability to make within-sound comparisons is similar to that of controls. These differences cannot be explained in terms of different time spans over which comparisons must be made. The results suggest unilateral neglect is linked to--if not actually determined by--a reduction in attentional capacity in both the visual and auditory domains, and across the dimensions of both space and time. The findings have potential clinical applications.
Journal of Cognitive Neuroscience 12/2000; 12(6):1056-65. · 5.18 Impact Factor
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ABSTRACT: The effect of asynchronous and nonsimultaneous interferers on detection of sinusoidal frequency modulation (FM) was compared with the effect of a synchronous interferer. In a two-interval, two-alternative forced-choice (2I-2AFC) adaptive procedure, listeners had to detect FM with a modulation frequency of 15 Hz, imposed on a 1-kHz sinusoidal carrier (the target). The 200-ms target was presented either alone (baseline condition), or with an interferer whose timing relative to the target was varied. The interferer was a 2.3-kHz sinusoidal carrier which was also frequency modulated at a rate of 15 Hz. Experiment one showed that thresholds for detection of FM increased significantly, both with a synchronous FM interferer, and also with asynchronous interferers (starting 200 ms before and stopping 200 ms after the target). Moreover, "gapped" interferers that were turned off during presentation of the target (presented for 200 ms before and for 200 ms after the target but not simultaneously) produced the same significant increase in thresholds as an asynchronous interferer that was not interrupted. In contrast, thresholds were not affected by the presence of a gapped unmodulated sinusoidal interferer. Experiment two showed that increasing the duration of the silent gap (centered on presentation of the target) between FM interferers from 200 to 600 ms did not abolish the interference. Thus nonsimultaneous FM interferers produced frequency modulation detection interference (FMDI) even when the silent gap between the interferers and target clearly led to the interferers and target being perceived as separate auditory objects. A possible explanation for the findings is the existence of an asymmetry in perception of steady and modulated sounds, as recently proposed by Cusack and Carlyon [Br. J. Audiol. 34.2, 112 (2000)]. Alternative explanations in terms of ringing in a hypothetical modulation filter bank and adaptation seem unlikely.
The Journal of the Acoustical Society of America 12/2000; 108(5 Pt 1):2329-36. · 1.55 Impact Factor
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ABSTRACT: The detection of slow (5 Hz) center-frequency modulations of formants (signals) can be impaired by the simultaneous presentation of off-frequency modulated formants (maskers) to the same ear [J. Lyzenga and R. P. Carlyon, J. Acoust. Soc. Am. 105, 2792-2806 (1999)]. In the present study we examine this "formant-frequency modulation detection interference (FMDI)" for various binaural masker presentation schemes. Signals and maskers were formantlike complex tones, centered around 1500 and 3000 Hz, respectively. Fundamentals of 80 and 240 Hz were used. The signals were presented to the right ear. The maskers were presented either to the right, the left, or to both ears, and they were either unmodulated or modulated at a slow rate (10 Hz). They had the same fundamental as the signals. Hardly any interference was found for the unmodulated maskers. For modulated maskers, the amount of FMDI depended strongly on the binaural masker presentation scheme. Substantial interference was found for the ipsilateral maskers. Interference was smaller for the contralateral maskers. In both cases the FMDI increased with increasing masker level. Substantial interference was also found for the binaural maskers. Imposing different interaural time and level differences (ITDs and ILDs) on maskers and signals did not affect FMDI. The same was true for the ITD condition when the maskers had different fundamentals than the signals, though FMDI was slightly smaller here. The amount of interference for the binaural maskers was roughly equal to that of the corresponding monaural masker with the largest effect. The data could not be described accurately using a model based on the loudness of the maskers. On the other hand, they were well described by a model in which the amount of FMDI was predicted from a "weighted combination" of the monaural masker levels.
The Journal of the Acoustical Society of America 09/2000; 108(2):753-9. · 1.55 Impact Factor
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ABSTRACT: Two experiments investigated the influence of resolvability on the perceptual organization of sequential harmonic complexes differing in fundamental frequency (F0). Using a constant-stimuli method, streaming scores for ABA-... sequences of harmonic complexes were measured as a function of the F0 difference between the A and B tones. In the first experiment, streaming scores were measured for harmonic complexes having two different nominal F0s (88 and 250 Hz) and filtered in three frequency regions (a LOW, a MID, and a HIGH region with corner frequencies of 125-625 Hz, 1375-1875 Hz, and 3900-5400 Hz, respectively). Some streaming was observed in the HIGH region (in which the harmonics were always unresolved) but streaming scores remained generally lower than in the LOW and MID regions. The second experiment verified that the streaming observed in the HIGH region was not due to the use of distortion products. Overall, the results indicated that although streaming can occur in the absence of spectral cues, the degree of resolvability of the harmonics has a significant influence.
The Journal of the Acoustical Society of America 08/2000; 108(1):263-71. · 1.55 Impact Factor
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ABSTRACT: Experiment 1 measured frequency modulation detection thresholds (FMTs) for harmonic complex tones as a function of modulation rate. Six complexes were used, with fundamental frequencies (F0s) of either 88 or 250 Hz, bandpass filtered into a LOW (125-625 Hz), MID (1375-1875 Hz) or HIGH (3900-5400 Hz) frequency region. The FMTs were about an order of magnitude greater for the three complexes whose harmonics were unresolved by the peripheral auditory system (F0 = 88 Hz in the MID region and both F0s in the HIGH region) than for the other three complexes, which contained some resolved harmonics. Thresholds increased with increases in FM rate above 2 Hz for all conditions. The increase was larger when the F0 was 88 Hz than when it was 250 Hz, and was also larger in the LOW than in the MID and HIGH regions. Experiment 2 measured thresholds for detecting mistuning produced by modulating the F0s of two simultaneously presented complexes out of phase by 180 degrees. The size of the resulting mistuning oscillates at a rate equal to the rate of FM applied to the two carriers. At low FM rates, thresholds were lowest when the harmonics were either resolved for both complexes or unresolved for both complexes, and highest when resolvability differed across complexes. For pairs of complexes with resolved harmonics, mistuning thresholds increased dramatically as the FM rate was increased above 2-5 Hz, in a way which could not be accounted for by the effect of modulation rate on the FMTs for the individual complexes. A third experiment, in which listeners detected constant ("static") mistuning between pairs of frequency-modulated complexes, provided evidence that this deterioration was due the harmonics in one of the two "resolved" complexes becoming unresolved at high FM rates, when analyzed over some finite time window. It is concluded that the detection of time-varying mistuning between groups of harmonics is limited by factors that are not apparent in FM detection data.
The Journal of the Acoustical Society of America 08/2000; 108(1):304-15. · 1.55 Impact Factor
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R P Carlyon
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ABSTRACT: Three experiments investigated whether or not the auditory system contains a neural mechanism that is sensitive to differences in the pattern of frequency modulation imposed on widely separated carriers. Experiment 1 measured the discrimination between an unmodulated two-tone complex and one in which either coherent or incoherent frequency modulation was imposed on the two carrier frequencies. These two frequencies were either 1100+1925 Hz or 1100+2000 Hz, and the stimuli were presented against a pink-noise background. The method was based on that used in experiments by Furukawa and Moore (1996), which were previously interpreted as providing evidence in favour of a mechanism sensitive to FM coherence. Discrimination was sometimes better for coherent than for incoherent FM, as reported by Furukawa and Moore, but only for four out of the eight listeners tested. The remaining experiments excluded those subjects who had shown no effect of FM coherence in experiment 1. Experiment 2 showed that detection of a static shift on the carrier frequencies of the two components was better when the carriers were shifted in the same, compared to the opposite, direction. This difference occurred regardless of whether the carriers were modulated coherently, incoherently, or were unmodulated. The experiment also showed that performance was better when the 1100-Hz carrier was shifted down and the 1925-Hz carrier was shifted up, compared to when the 1100-Hz carrier shifted up and the 1925-Hz carrier shifted down. Experiment 3 showed that this difference also applied to dynamic changes: detection of quasi-linear frequency sweeps (0.5 cycles of sinusoidal FM) was better when the higher component glided up and the lower component glided down than vice versa. In the former condition, performance was as good as with same-direction sweeps. It is concluded that the effects observed in experiment 1 and by Furukawa and Moore result from the processing of a global percept arising from the perceptual fusion of the two carriers, and do not represent an across-frequency mechanism sensitive to FM coherence. In addition, it is argued that experiments 2 and 3 demonstrate the existence of perceptual asymmetries in hearing.
Hearing Research 03/2000; 140(1-2):173-88. · 2.70 Impact Factor
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ABSTRACT: In a two-interval, two-alternative, forced-choice (2I-2AFC) adaptive procedure, listeners discriminated between the fundamental frequencies (F0s) of two 100-ms harmonic target complexes. This ability can be impaired substantially by the presence of another complex (the "fringe") immediately before and after each target complex. It has been shown that for the impairment to occur (i) target and fringes have to be in the same frequency region; (ii) if all harmonics of target and fringes are unresolved then they may differ in F0; otherwise, they have to be similar [C. Micheyl and R. P. Carlyon, J. Acoust. Soc. Am. 104, 3006-3018 (1998)]. These findings have been discussed in terms of information about the fringe's F0 being included in the estimate of the F0 of the target, and in terms of auditory streaming. The present study investigated the role of perceived location and ipsilateral versus contralateral presentation of the fringes on F0 discrimination of the target. Experiment 1 used interaural level differences (ILDs), and experiment 2 used interaural time differences (ITDs) to create a range of lateralized perceptions of the 200-ms harmonic fringes. Difference limens for the F0 of the monaural target complex were measured in the presence and absence of the fringes. The nominal F0 was 88 or 250 Hz and could be the same or different for target and fringes. Stimuli were bandpass filtered between 125-625, 1375-1875, or 3900-5400 Hz. In both experiments, the effect of the fringes was reduced when their subjective location differed from that of the target. This reduction depended on the resolvability of both the fringes and the target. The effect of the fringes was reduced most (but still present), when fringes were presented purely contralaterally to the target. The results are consistent with the idea that the fringes produce interference when the listeners have difficulty segregating the target from the fringes, and that a difference in perceived location enhances segregation of the sequentially presented stimuli.
The Journal of the Acoustical Society of America 12/1999; 106(6):3553-63. · 1.55 Impact Factor
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ABSTRACT: Vowels are characterized by peaks in their spectral envelopes: the formants. To gain insight into the perception of speech as well as into the basic abilities of the ear, sensitivity to modulations in the positions of these formants is investigated. Frequency modulation detection thresholds (FMTs) were measured for the center frequency of formantlike harmonic complexes in the absence and in the presence of simultaneous off-frequency formants (maskers). Both the signals and the maskers were harmonic complexes which were band-pass filtered with a triangular spectral envelope, on a log-log scale, into either a LOW (near 500 Hz), a MID (near 1500 Hz), or a HIGH region (near 3000 Hz). They had a duration of 250 ms, and either an 80- or a 240-Hz fundamental. The modulation rate was 5 Hz for the signals and 10 Hz for the maskers. A pink noise background was presented continuously. In a first experiment no maskers were used. The measured FMTs were roughly two times larger than previously reported just-noticeable differences for formant frequency. In a second experiment, no significant differences were found between the FMTs in the absence of maskers and those in the presence of stationary (i.e., nonfrequency modulated) maskers. However, under many conditions the FMTs were increased by the presence of simultaneous modulated maskers. These results indicate that frequency modulation detection interference (FMDI) can exist for formantlike complex tones. The FMDI data could be divided into two groups. For stimuli characterized by a steep (200-dB/oct) slope, it was found that the size of the FMDI depended on which cues were used for detecting the signal and masker modulations. For stimuli with shallow (50-dB/oct) slopes, the FMDI was reduced when the signal and the masker had widely differing fundamentals, implying that the fundamental information is extracted before the interference occurs.
The Journal of the Acoustical Society of America 06/1999; 105(5):2792-806. · 1.55 Impact Factor
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ABSTRACT: Variations in the amplitude of transiently evoked otoacoustic emissions (TEOAEs) produced by a contralateral complex tone were measured in 26 normal-hearing human subjects. TEOAEs were evoked using a 1-kHz tone pip at 60 dB SPL. The contralateral complex consisted of harmonic components with frequencies between 400 and 2000 Hz; it was presented at levels ranging from 40 to 50 dB SL and its fundamental frequency (F0) was varied. In experiment 1, the dependence of TEOAE amplitude variations on the F0 of the contralateral complex was measured by varying the F0 from 50 to 400 Hz in octave steps. The results revealed a nonmonotonic dependence of TEOAE amplitude variations on contralateral F0, with significantly larger TEOAE suppression for F0's of 100 and 200 Hz than for F0's of 50 and 400 Hz. Experiment 2, in which the harmonics were summed in alternating sine-cosine phase instead of constant sine phase, showed a shift of the function relating TEOAE attenuation to F0 towards lower F0's, indicating that the waveform repetition rate, rather than harmonic spacing, was the actual factor of the dependence of contralateral TEOAE attenuation on F0. Furthermore, significantly smaller suppression was observed with the alternating-phase complexes than with the sine-phase complexes, suggesting an influence of the waveform crest factor. Experiment 3 showed no difference between the contralateral TEOAE attenuation effects produced by positive and negative Schroeder-phase complexes. Overall, these results bring further arguments for the notion that contralaterally induced medial olivocochlear bundle (MOCB) activity, as measured through the contralateral suppression of TEOAEs in humans, is sensitive to the rate of temporal envelope fluctuations of the contralateral stimulus, with preferential rates around 100-200 Hz.
The Journal of the Acoustical Society of America 02/1999; 105(1):293-305. · 1.55 Impact Factor
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ABSTRACT: Listeners were required to detect mistuning imposed on the center ("target") component of a 200-ms complex consisting of the first seven harmonics of a 500-Hz fundamental. In the standard interval of each 2IFC trial, all components were frequency modulated in-phase by a 5-Hz sinusoid. In the signal interval the frequency modulation of the target component was inverted in-phase, thereby introducing a mistuning proportional to the depth of FM. In a similar experiment, using monaural presentation, Carlyon [J. Acoust. Soc. Am. 95, 2622-2630 (1994)] reported a substantial elevation of thresholds in the presence of an unmodulated asynchronous interferer with frequency identical to the mean frequency of the target. This was attributed to the interferer, causing the target component to be perceptually segregated from the remainder of the complex, thereby impairing across-frequency comparisons. Experiment 1 of the present study showed that an interferer presented contralaterally for 200 ms before and 100 ms after the signal complex (no simultaneous presentation) also impaired performance, but to a lesser extent than an ipsilaterally presented one. Experiment 2 showed that an interferer which was presented dichotically with an interaural level difference (ILD) of 10 dB, so that it was perceived contralaterally, had the same (large) effect as if it were presented ipsilaterally. Experiment 3 showed that, in the absence of any interferer, performance was impaired when the nontarget components were presented contralaterally to the target component. However, performance was not impaired when the nontarget components were presented dichotically with an ILD of 20 dB, so that they were perceived contralaterally to the target component. It is concluded that the level of performance in the mistuning task is determined by whether the target is presented to the same ear as the rest of the complex, rather than by its perceived location.
The Journal of the Acoustical Society of America 01/1999; 104(6):3534-45. · 1.55 Impact Factor
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ABSTRACT: It has recently been shown that the ability of listeners to encode the F0 of a "target" harmonic complex can be disrupted by another complex (the "fringe") presented immediately before and after it [R. P. Carlyon, J. Acoust. Soc. Am. 99, 525-533 (1996)]. This finding has been attributed to listeners overintegrating information about the fringe's F0 when estimating that of the target. Here difference limens for F0 (DLF0s) for a 100-ms harmonic complex target were measured using a two-interval two-alternative forced choice (2I-2AFC) adaptive procedure, in the presence and absence of 200-ms harmonic fringes. The target F0s in the signal and standard intervals were geometrically placed around a nominal F0 of 88 or 250 Hz; the fringe F0, constant throughout a block, was set at either of these two frequencies. The harmonics were bandpass filtered into one of three different frequency regions: low (125-625 Hz), mid (1375-1875 Hz), or high (3900-5400 Hz). In the low and mid regions, the fringes produced a large increase in DLF0s when they had a similar F0 to the target. This effect was absent or greatly reduced when the fringes and targets either had widely different F0s or occupied different frequency regions, and it was not reduced by providing additional spectral cues to the transition between fringes and targets. In the high region, the fringes produced large increases in DLF0s whether or not their F0 was similar to that of the targets. It is concluded that these results reflect a process of overintegration which, in the low and mid regions, is sensitive both to the F0 and to the spectral region of the stimuli. It is suggested that the different results in the high region may reflect the fact that, unlike in the low or mid regions, all the components of the targets and fringes were unresolved by the peripheral auditory system. Finally, the results of all the experiments are discussed in terms of auditory streaming.
The Journal of the Acoustical Society of America 12/1998; 104(5):3006-18. · 1.55 Impact Factor
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ABSTRACT: The pitch strength of rippled noise and iterated rippled noise has recently been fitted by an exponential function of the height of the first peak in the normalized autocorrelation function [Yost, J. Acoust. Soc. Am. 100, 3329-3335 (1996)]. The current study compares the pitch strengths and autocorrelation functions of rippled noise (RN) and another regular-interval noise, "AABB." RN is generated by delaying a copy of a noise sample and adding it to the undelayed version. AABB with the same pitch is generated by taking a sample of noise (A) with the same duration as the RN delay and repeating it to produce AA, and then concatenating many of these once-repeated sequences to produce AABBCCDD.... The height of the first peak (h1) in the normalized autocorrelation function of AABB is 0.5, identical to that of RN. The current experiments show the following: (1) AABB and RN can be discriminated when the pitch is less than about 250 Hz. (2) For these low pitches, the pitch strength of AABB is greater than that for RN whereas it is about the same for pitches above 250 Hz. (3) When RN is replaced by iterated rippled noise (IRN) adjusted to match the pitch strength of AABB, the two are no longer discriminable. The pitch-strength difference between AABB and RN below 250 Hz is explained in terms of a three-stage, running-autocorrelation model. It is suggested that temporal integration of pitch information is achieved in two stages separated by a nonlinearity. The first integration stage is implemented as running autocorrelation with a time constant of 1.5 ms. The second model stage is a nonlinear transformation. In the third model stage, the output of the nonlinear transformation is long-term averaged (second integration stage) to provide a measure of pitch strength. The model provides an excellent fit to the pitch-strength matching data over a wide range of pitches.
The Journal of the Acoustical Society of America 11/1998; 104(4):2307-13. · 1.55 Impact Factor
