摘要:

Traditionally, auditory spectral resolution is studied psychophysically by masking experiments (i.e., the effect of a masking stimulus on the detection threshold of a test tone with variable frequency). During the last decade there has been increasing experimental evidence of an essential qualitative difference between the results of two classes of such experiments: (a) masking stimulus and test tone being presented simultaneously (direct masking) or (b)nonsimultaneously (forward masking, pulsation threshold). This difference can be interpreted as an effect of lateral suppression (spectral sharpening) which manifests itself only in case of nonsimultaneous presentation of masking stimulus and test tone. An overview of the relevant data is presented (e.g., auditory Mach bands, two‐tone suppression, increased ripple resolution, etc.), with occasional references to related electrophysiological data. The experimental data lead to the notion of a peripheral stage of spectral sharpening of such a nature that it does not affect the detection threshold of a test tone in direct masking.

ISSN:0001-4966    

DOI:10.1121/1.2016538

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The nonsimultaneous masking of a sinusoidal signal (2 kHz) produced by a critical‐band noise (200 Hz wide centered at 2 kHz) is reduced by the presence of a suppressor (bandpass noise, 2300–3700 Hz) during the masker interval. The results of various experiments suggest: (1) Suppression is greater in backward masking than in forward masking. (2) The effect of masker intensity on suppression differs in backward and forward masking. (3) If the suppressor is presented to the contralateral ear, suppression is observed in backward masking but not in forward masking. These experimental differences may reflect a fundamental difference in the processes underlying backward and forward masking. (4) The amount of masking decreases with an increase in the duration of the suppressor. It also decreases with an increase in the duration of a reduction in the intensity of the excitor presented alone. However, this change in masking is markedly different for the two conditions; the effect of the suppressor is not simply to reduce the effective level of the excitor. [Research supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.2016589

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Synthetic steady‐state vowels from an /i/‐/I/‐/ / continuum were presented in an AX discrimination task. The interval between the stimuli in a pair was either short (240 ms) or long (1920 ms), and either empty or filled with irrelevant vowel sounds. Discrimination performance was disturbed by both these manipulations, suggesting that auditory memory is subject to decay as well as to interference. In a second experiment, we predicted discrimination performance at short‐unfilled and long‐filled intervals from identification response to the same AX pairs. While obtained discrimination performance exceeded the predictions, this difference was equally small at the two interstimulus intervals. Identification was as much affected by interstimulus interval as discrimination: There were large contrast effects at the short‐unfilled interval, but not at the long‐filled interval. Implications of these results for models of categorical perception will be discussed. [Work supported by NICHD.]

ISSN:0001-4966    

DOI:10.1121/1.2016636

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Consonantal environment may aid in specifying vowel identity by supplying critical information about timing. Several vowel pairs in American English are distinguished by temporal as well as spectral variables, and these temporal differentia vary with articulatory rate. Two studies were designed to explore the following paradox: When consonantal formant transitions are introduced into a steady‐state vowel, holding syllable duration constant, a response shift is observed toward longer‐vowel alternatives, even though steady‐state duration has been reduced. The first study verified this finding for the vowel pair /ε/‐/æ/ in comparisons of ♯V♯ and bVb continua. Pairs of continua were defined separately byF1 variation and by duration variation, and each continuum type evidenced the paradox. A second study varied the rate of symmetric consonantal transitions inF1‐varying CVC continua (V = /ε, æ/, C = ♯, b, w/) in order to test whether transition rate might specify an articulatory rate that effectively scales vowel duration. Vowel responses did not vary monotonically with either transition rate or steady‐state duration, but interacted with the perceived identity of the initial consonant. Listeners' judgments may demonstrate a sensitivity to constraints on the relative timing of consonantal and vocalic gestures. [This work was supported by NIH grant HD‐01994 to Haskins Laboratories, and by the University of Michigan Society of Fellows.]

ISSN:0001-4966    

DOI:10.1121/1.2016687

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

As a continuation of our studies on the psychophysical bias in the judgment of vowel pitch (Chuang and Wang. ASA 60.1 and 62.1) and duration (Wanget al.ASA 60.1), this study was aimed at quantitative investigation of perceptual bias in the loudness dimension. The experimental design and the four vowels [i,e,u, and ɑ] were the same as previous studies with [ɑ]as the reference. The perceptual loudness bias differences were obtained by equalizing the syllabic speech power of the four test vowels. The mean loudness difference, based upon data gathered from 12 listeners, indicated that in reference to [ɑ], [i]was 7.1 dB, [e] was 4.5 dB, and [u]was 3.8 dB louder, respectively. These results give quantitative support to the studies of Ladefoged (1961) and Allen (1971) which showed qualitatively that with speech power normalization, the high vowels [i] and [u]were judged louder than the lower vowel [ɑ]. Furthermore, these perceptually obtained loudness differences are found to be inversely matched to the reported intensity difference of sustained vowels (Lehiste and Peterson, 1958). The negative correlation between the production intensity and the perceptual judgment of loudness in congruent with results reported in our previous pitch and duration studies. [Work supported by NSF grant BNS 76‐00017 and partially supported by NS 13274.]

ISSN:0001-4966    

DOI:10.1121/1.2016741

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Generally speaking, the important perceptual information in a signal is carried by the modulation of the envelope (more precisely, of the envelopes after critical‐band filtering, to account for auditory spectral analysis). In relation to speech transmission in enclosures this leads to the notion that loss of intelligibility is related to loss of the original envelope modulations. The degree of modulation loss caused by an enclosure (reverberation, interfering noise) can be quantified objectively by the modulation transfer function (MTF). Experimentally, for a variety of conditions, the MTF was found to correlate well with intelligibility scores obtained with talkers and listeners. The MTF, as a powerful predictor of speed intelligibility, can be obtained either from direct measurements in concrete situation, or from calculations in the design stage of a room or auditorium.

ISSN:0001-4966    

DOI:10.1121/1.2016789

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The acoustical qualities of an auditorium are highly dependent on the listener's own subjective judgments. Correlation between such judgments and measurable acoustical properties has been sought by numerous workers. New and complex measurements have been experimented with, but interpretation remains difficult. Without really breaking new ground, the acoustics of some recently completed auditoria were evaluated by simply measuring (1) the reverberation times, (2) the loudness, and (3) the background noise levels, and by relating the results to “preferred” standards. Ultimate judgment was left to the listener. This paper discusses these measurements and their interpretation, as presented to the layman.

ISSN:0001-4966    

DOI:10.1121/1.2016839

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

A brief review is made of previous single‐number rating development with emphasis on the sound transmission class (STC). A single‐number metric, called Exterior Wall Noise Rating (EWNR), has been developed in a similar, but independent, manner such that theA‐weighted interior noise level, due to highway noise sources, can be estimated directly from the value of EWNR and theA‐weighted exterior noise level. The development is defined first in terms of the basic theory for noise reduction from outdoors to indoors in a single frequency band. The overall effective noise reduction is a summation of these values over many frequency bands. The EWNR single‐number rating replaces this complex summation and provides a greatly simplified calculation procedure. In addition, the EWNR can be used for direct comparisons of the noise insulation properties of exterior building elements. The EWNR metric is applicable to other exterior noise sources if the proper adjustment factors are included. Results are shown from recently conducted field tests which indicate good accuracy for predicting interior noise levels due to aircraft noise sources.

ISSN:0001-4966    

DOI:10.1121/1.2016884

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Studies are continuing on the use of long, low‐loss optical fibers as direct acoustic sensors [J. A. Bucaro, E. F. Carome, and M. R. Layton, J. Acoust. Soc. Am.62, S72 (1977)]. Currently we are employing a single‐path coiled‐fiber system and examining in detail acoustically induced variations in the transmitted light intensity. We have detected effects that we attribute to changes in the intensity of the light propagated in a particular fiber mode. Details of the experimental technique employed and quantitative data on these effects will be presented. [Supported in part by Office of Naval Research.]

ISSN:0001-4966    

DOI:10.1121/1.2016889

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

In this paper a weak finite‐amplitude solution for the difference‐frequency field of a parametric acoustic array is derived via the second‐order nonlinear paraxial wave equation [i.e., the nonlinear optical analog established by E. A. Zabolotskaya and R. V. Khokhlov, Soy. Phys. Acoust.15, 35–40 (1969)] by expressing the primary waves of an axisymmetrically excited bifrequency piston projector as a weighted sum of Gauss‐Laguerre modes. By relating the fundamental (i.e., Gaussian) modes in the farfield of the projector to those of equivalent “Bessel beams” a new closed‐form expression for the difference‐frequency field is thus obtained as a function of range. A review of the solution's phenomenological properties will then be presented, followed by a brief comparison of predicted results and experimental data reported in the literature.

ISSN:0001-4966    

DOI:10.1121/1.2016497

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP