摘要:

Three experiments were completed to examine the effect of masker duration and spectrum on forward-masked intensity discrimination. Four listeners participated in each experiment. Intensity discrimination was measured in quiet and in the presence of forward maskers using adaptive forced-choice procedures. The standard duration was either short (10 ms) or long (250 ms) in experiment 1 and short (10 ms) in experiment 2. The standard always occurred 100 ms after the offset of the masker. In the first experiment employing 1.0-kHz maskers and standards, a short duration masker (10 ms) produced more masking than a long duration masker (250 ms). A mid-level elevation of the Weber fraction was observed for all conditions. To ensure that the results of experiment 1 were not influenced by off-frequency listening, the second experiment employed a broadband noise masker. As before, a short duration (10 ms) masker produced more masking than a long duration masker (100 ms) and a mid-level elevation of Weber fractions was observed. This outcome is inconsistent with a peripheral sensory effect for which an increase in masker duration should result in a greater amount of adaptation, and, as a consequence, more masking. A third experiment employing a broadband noise masker and standard showed the greatest amount of masking for low-level standards, but only when the duration of the masker and standard was short. This result is similar to one seen for a single listener in the first experiment for short duration tonal maskers and standards. For this listener, a second tone presented at 4.133 kHz presented simultaneously with the 1.0-kHz masker reduced significantly the amount of masking for low-level standards, but the mid-level elevation of the Weber fraction remained. Taken together, these results suggest that perceptual similarity plays a role in forward-masked intensity discrimination but does not account entirely for the mid-level elevation of the Weber fraction.

ISSN:0001-4966    

DOI:10.1121/1.419610

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

In an effort to evaluate the importance of across-frequency comparisons of envelope patterns in comodulation masking release (CMR) experiments and to compare joint effects of target–masker frequency separation for both CMR and modulation detection interference (MDI) tasks, thresholds were measured for three tasks. These tasks were: (a) the detection of sinusoidal amplitude modulation (SAM) of a tone, (b) the detection of a reduction in the modulation depth of a fully modulated SAM tone, and (c) the detection of a tone added to a narrow band of noise. Thresholds were obtained for the target alone and for the target presented with two maskers. For the detection of SAM, thresholds did not depend on whether the modulation patterns of the target and masker elements were the same or random. For the latter two tasks, modulator phase effects were apparent for target–masker frequency separations less than 1–2 oct. In contrast, past work has shown that observers can compare modulator envelope phases across frequency separations larger than 1–2 oct [Strickland et al., J. Acoust. Soc. Am.86, 2160–2166 (1989); Yost and Sheft, J. Acoust. Soc. Am.85, 848–857 (1989)]. In a second experiment, thresholds for the detection of SAM were obtained after prolonged exposure to a fully modulated SAM tone. For four of the five observers, modulation-rate specific adaptation was obtained for test/adapting carrier-frequency separations approaching 2 oct below and 1 oct above the adaptor.

ISSN:0001-4966    

DOI:10.1121/1.419719

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Green and Dai [ inAuditory Physiology and Perception, edited by Y. Cazals, L. Demany, and K. Horner (Pergamon, Oxford, 1992)] reported a series of experiments which suggested that listeners’ ability to perform simultaneous across-frequency comparisons of intensity is severely impaired when the target and flanking components begin or end at different times. The present experiment sought to replicate the effect of onset asynchrony and included an additional condition in which the leading portion of the asynchronous target component was accompanied by a pair of “captor” tones. The intended purpose of the captor tones was to promote a perceptual organization in which the leading and synchronous portions of the asynchronous target component were grouped with different auditory objects. For all six listeners an asynchrony of 320 ms raised thresholds substantially relative to the synchronous onset condition, the magnitude of the increase ranging between 6 and 16 dB. By contrast, the mean elevation of threshold in the presence of the captor was only 3 dB, although for all listeners thresholds were still greater than for the synchronous onset condition. The results support the view that the deleterious effect of onset asynchrony on profile analysis performance is due to the operation of auditory grouping principles.

ISSN:0001-4966    

DOI:10.1121/1.419720

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Several studies have recently demonstrated that normal-hearing listeners are sensitive to short-term temporal asymmetry in the envelopes of sinusoidal or noise carriers. This paper presents a study in which cochlear implantees were presented trains of current pulses with temporally asymmetric envelopes through one channel of an implant that stimulates the auditory nerve directly, thereby bypassing cochlear processes. When the level of the stimuli was adjusted to fit their audibility range, the implantees were able to discriminate temporal asymmetry over a much wider range than normal-hearing listeners. The results suggest that the perception of temporal asymmetry is limited by compression in the normal cochlea.

ISSN:0001-4966    

DOI:10.1121/1.419721

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Four experiments investigated memory for timbre using the interpolated-tone paradigm [Deutsch, Science168, 1604–1605 (1970)], in which participants discriminate pairs of tones (standard and comparison) separated by intervening (interpolated) tones. Interpolated tones varied from the standard tone in spectral similarity (within-dimensional variation), fundamental frequency (cross-dimensional variation), and repetition frequency. While the latter two variables had negligible effects on timbre memory, interference with timbre memory increased with the spectral similarity of the interpolated tones to the standard tone. The findings closely parallel those found for pitch memory, and suggest that memory interference depends on perceptual similarity in both cases.

ISSN:0001-4966    

DOI:10.1121/1.419722

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Psychophysical studies have been completed with two binaural cochlear implant patients. In our earlier studies [van Hoesel et al., J. Acoust. Soc. Am.  94, 3178–3189 (1993); R. J. M. van Hoesel and G. M. Clark, Ann. Otol. Rhinol. Laryngol. Suppl. 106  104, 233–235 (1995)], lateralization experiments showed good sensitivity to interaural amplitudes but poor sensitivity to interaural time delays when compared with normal hearing subjects. In the studies presented here, both temporal and binaural intensity interactions were further explored. Interaural time delay (ITD) perception was investigated using direct measurement of the just-noticeable difference (jnd) in ITD. Both rate and place of stimulation were varied. Binaural rate discrimination was measured and compared with monaural rate perception. Binaural intensity interaction was explored for matched and unmatched place conditions by means of loudness summation and central masking studies. Results showed that ITDs for interaural time delays were large when compared to normal hearing, even when place of stimulation on each of the two sides was carefully matched. The jnds in ITD were similar for stimulation rates from 50 to 200 pps, and increased at 300 pps. Rate difference limens experiments showed similar results for diotic and monaural stimuli, but improved jnds for dichotic presentation at stimulation rates below 150–200 pps. Binaural intensity interactions showed loudness summation effects with both patients, for matched as well as unmatched place conditions. Central masking was also observed with both subjects, although it was not found to be place dependent.

ISSN:0001-4966    

DOI:10.1121/1.419611

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

This study examined the average and individual performance over time of 49 adult cochlear implant subjects. Subjects were randomly assigned to receive either the Ineraid cochlear implant, with analog processing, or the Nucleus cochlear implant, with feature-extraction processing. All subjects had postlingual profound bilateral sensorineural hearing loss and received no significant benefit from hearing aids before implantation. Group data were examined in two ways. First, only subjects who had complete data over the test period were examined. Second, an analysis of all available data was carried out by mixed linear-model analysis. In this analysis, to account for missed follow-ups at the planned intervals, data consisting of the observations closest in time to the planned test times were modeled by natural splines with knots at the planned follow-up times. Contrasts between all pairs of planned follow-up times for each device were tested, as were contrasts between devices at each planned follow-up time. Results indicated little difference between the performance of the Ineraid and Nucleus subjects in their level of performance or their rate of learning. Postimplantation performance was typically superior to preimplantation performance within 9 months, and continued to improve up to 18–30 months depending on the speech perception measure. In some subjects, improvements in speech perception measures were observed up to four or five years postimplantation. There was also evidence that three subjects had a decrement in overall speech perception performance, although their postimplantation scores were always higher than their preimplantation scores. In at least one subject this was likely a result of age-related cognition decrements.

ISSN:0001-4966    

DOI:10.1121/1.419724

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

The present study investigated the articulatory control of the German vowel quantity contrast, i.e., the phonological difference between short and long vowels. By means of an optoelectronic system the excursions of the compound lower lip/jaw opening and closing gestures were measured during production of test sentences comprising the target sequence /pVp/ (V=/a/,/i/, /u/, /a:/, /i:/, /u:/). First, a highly linear relationship between peak velocity and movement amplitude emerged within each quantity class. Second, vowel quantity systematically influenced the scaling of velocity and amplitude during oral opening. Third, as compared to their short counterparts, long vowels showed an increased peakedness of the velocity profile. Finally, the velocity profiles of the long vowels were characterized by an asymmetric shape in terms of a prolonged deceleration phase of the opening and a lengthened acceleration interval of the closing movement. With respect to durational coarticulation patterns, the control of vowel quantity clearly differed from intrinsic, i.e., vowel type-induced, variability. The latter was partially compensated for at the level of word duration by shortening of the prevocalic consonant whereas vowel quantity turned out to be primarily due to the lengthening of the syllable /pV/.

ISSN:0001-4966    

DOI:10.1121/1.419725

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

The quantity, harmonic-to-noise ratio (HNR), has been used to estimate the level of noise in human voice signals. HNR estimation can be accomplished in two ways: (1) on a time-domain basis, in which HNR is computed directly from the acoustic waveform; and (2) on a frequency-domain basis, in which HNR is computed from a transformed representation of the waveform. An algorithm for computing HNR in the frequency domain was modified and tested in the work described here. The modifications were designed to reduce the influence of spectral leakage in the computation of harmonic energy, and to remove the necessity of spectral baseline shifting prescribed in one existing algorithm [G. de Krom, J. Speech Hear. Res.36, 254–266 (1993)]. Frequency-domain estimations of HNR based on this existing algorithm and our modified algorithm were compared to time-domain estimations on synthetic signals and human pathological voice samples. Results indicated a highly significant, linear correlation between frequency- and time-domain estimations of HNR for our modified approach.

ISSN:0001-4966    

DOI:10.1121/1.419726

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

The magnitude and temporal extent of consonantal and vocalic coarticulation are reported for VCV sequences with two vowels (/i/, /a/) and seven consonants (/p/, /n/, dark /l/, /s/, /∫/, /ɲ/,/k/). Different degrees of articulatory constraint, or DAC values, are assigned to the consonants and vowels based on knowledge of their articulatory properties, in particular, the degree of involvement of the tongue dorsum in closure or constriction formation. Mean results on dorsopalatal contact andF2frequency for five speakers of the Catalan language are presented. Predictions based on the DAC value for consonants and vowels account satisfactorily for the C-to-V effects (e.g., those for /ɲa/ are more prominent that those for /pi/); moreover, vowel-dependent effects tend to be negatively correlated with the DAC value for the consonant (e.g., they are more prominent when the intervocalic consonant is /p/ than when it is dark /l/). V-to-C effects are also conditioned by the tongue-dorsum position for the consonantal gesture. Coarticulatory directionality trends reveal that the extent to which the vowel-dependent tongue-dorsum activity may be anticipated is closely linked to the mechanico-inertial constraints associated with the tongue dorsum during consonantal production; this observation explains the salience of the vowel-dependent anticipatory effects in VCV sequences favoring C-to-V anticipation and of the vowel-dependent carryover effects in VCV sequences giving special weight to C-to-V carryover.

ISSN:0001-4966    

DOI:10.1121/1.419727

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP