摘要:

Signals, received at two (or more) locations, and originating from a remote acoustic point source, exhibit time delay(s) that are useful for estimating source location or receiver geometries. Consequently, numerous procedures have been proposed for passive time‐delay estimation in such cases. Past investigations apply, however, only when source and receiver motion is negligible. This paper extends previous results for maximum‐likelihood (ML) estimation of time delay to the situation where the source, or the receivers, or both are in motion. It is shown that in the simplest case with two receivers, one of the signals must be appropriately time scaled prior to computing a generalized cross correlation of the received signals.

ISSN:0001-4966    

DOI:10.1121/1.381467

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

A general formulation of the problem of extracting information about random wave sources is presented. The formulation places no restrictions upon the complexity of the propagation and applies to any situation where the propagation may be adequately described by a deterministic Green’s function. It is shown that the general problem may be cast into the form of an integral equation, the kernel of which contains the physics of the propagation and the solution of which describes the location and spectral content of all sources. The special case of a homogeneous medium is examined in detail, and it is shown that conventional processing techniques may be viewed as attempts to solve an approximate version of the integral equation. An exact formal solution for the case of an arbitrary medium is derived. This formal solution, although it may not be implementedperse, is nonetheless expressed in such a form that a useful procedure for generating approximate solutions is suggested. This procedure, which is a generalized version of beamforming, may then be used to investigate limitations on the performance of hypothetical systems imposed by only approximate knowledge of the propagation and by observation of the transmitted wave field over only a limited spatial domain.

ISSN:0001-4966    

DOI:10.1121/1.381468

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

A new method for measuring electrical‐impedance changes that are elicited by tonal stimuli in the cochlea of the anesthetized guinea pig has been developed. Constant‐amplitude currents of low‐frequency sinusoidal waveform are delivered to scala media simultaneously with tonal stimuli. In the signal recorded from scala media, energy is detected at frequencies equal to the sum and difference of the applied frequencies. This energy is interpreted as due to changes ΔRin the resistance of the scala media that are synchronized with the acoustic waveform. The maximum magnitude of the change varies from about 0.2% in turn I to about 1% in turn III. During normal conditions, striking parallels exist between the behavior of ΔRandCMas both frequency and intensity are varied. However, under asphyxic conditions, the observed change in ΔRis usually much less than that inCM. The results are shown to be qualitatively, though not quantitatively, consistent with a two‐dimensional, variable‐resistance model of the cochlea.

ISSN:0001-4966    

DOI:10.1121/1.381469

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

With an impulse response technique the transfer functions from the free sound field to the ear‐canal entrance were measured on 20 subjects for sound incidence from ten directions of the symmetry plane and 20 directions of the horizontal plane. Separate for each direction amplitude and phase of these transfer functions were averaged using a technic, which yields mean values still containing fine structures of single measurements. Additionally the transfer function of the ear canal was measured on three subjects. The eardrum impedance was then computed from this transfer function and completes the poor knowledge of the eardrum impedance in the frequency range from 2 to 15 kHz.

ISSN:0001-4966    

DOI:10.1121/1.381470

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

This paper reports the results of further experiments on two‐interval roving‐level intensity discrimination and on the dependence of resolution and bias on level within the range of roving levels (the resolution and bias edge effects). The experimental parameters considered are the intensity rangeR, the intersignal durationT, and the pulse durationTp. In order in obtain a picture of the natural bias, no feedback was presented. The results on the dependence of resolution on level are compared to previous results of the same type obtained from one‐interval identification experiments. Discrepancies between the experimental results and the preliminary theory of intensity resolution [ Durlach and Braida, J. Acoust. Soc. Am. 46, 372–383, (1969)] are identified and implications of the data for an improved theory aree discussed.

ISSN:0001-4966    

DOI:10.1121/1.381471

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Experimental results are described for the dependence on interaural stimulus parameters of subjective lateral‐position matches and just‐noticeable differences (jnd’s) in interaural amplitude and time. All experiments employed 500‐Hz tones presented through acoustically monitored headphones. The overall amplitudes of the stimuli were iteratively adjusted to eliminate subjective loudness cues in the interaural‐amplitude jnd experiments. Performance in the experiments is analyzed within the framework of a probabilistic lateralization model in which internal noise is explicitly treated. The model predicts a specific relation between position matches and the interaural amplitude and time jnd’s. The data are qualitatively consistent with the predictions, and the quantitative agreement is good for one subject, moderate for the second, and poor for the third. In particular, the model predicts the observed asymmetry in the dependence of the interaural‐time jnd on interaural time delay for nonunity interaural amplitude ratios. Calculated values of the internal noise of the subjective image position are in qualitative agreement with reports by observers of image diffuseness as a function of interaural parameters of the stimulus.

ISSN:0001-4966    

DOI:10.1121/1.381472

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Intensity and frequency discrimination were measured at three signal frequencies for stimuli presented (1) binaurally, in phase, (2) monaurally, to the left ear, and (3) monaurally, to the right ear. The binaural difference limens (DL’s) are uniformly smaller than the monaural DL’s for both intensity and frequency discrimination at all frequencies. The size of the effect is within the range that is predicted by either an information‐integration or an independent‐threshold model.

ISSN:0001-4966    

DOI:10.1121/1.381446

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Lateralization performance was measured as a function of signal duration using two‐tone complexes of varying frequency separation, all centered at 3500 Hz. Acoustic integration occurs for this task, but the improvement with increasing duration is less rapid than would be expected were the subjects’ performance based on the number of opportunities available per trial to observe the value of the interaural time difference.

ISSN:0001-4966    

DOI:10.1121/1.381473

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Data on time response in the nervous system are available for animals. Rate‐matching data for humam subjects with implanted electrodes are available. These data do not tell us with certainty up to what rate people with normal hearing utilize time information directly. In many experiments an attempt to measure time response is confused by the presence of spectral clues. Short‐term spectral clues exist in stochastic sequences of positive and negative pulses and in modulated white noise, both of which have a white long‐term spectrum. These clues are periodicity (with a period equal to the pulse or modulation rate) and symmetry (about frequencies equal to integer multiples of half this rate), differences at different frequencies in the peak‐ or rms‐voltage distribution function of the output of a narrow‐band filter and, in the case of stochastic pulse sequences, differences in extreme intensity at different frequencies. It may be that the ability to match at high rates and the perception of tonal quality that subjects with excellent and trained hearing, such as musicians, exhibit for white‐spectrum stochastic pulse sequences or gated noise is due to the residue phenomenon or to spectral clues discussed in this paper.

ISSN:0001-4966    

DOI:10.1121/1.381437

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

An investigation to determine the significance of formant frequencies, pitch, and source‐spectrum slope on voice classification is reported. Eight professional singers sang five common vowels on four common pitches, and, in a forced‐choice test, vocal pedagogues classified the vocalization as tenor, baritone, or bass. Formant frequency and pitch differences accounted for most of the jury‐ evaluation results. To evaluate more accurately the significance of formant frequencies, pitch, and voicing and source‐spectral slope on voice classification, vowel synthesis was employed. Measurements of spoken vowel vocalizations revealed higher formant frequencies in tenor timbre type and lower formant frequencies in bass timbre type. Long‐time‐average spectra seem to afford a good estimate of voice classification. Formant‐frequency percentage differences between basses and tenors were similar to those found between males and females, suggesting that the mouth and pharynx lengths, known to differentiate females and males, probably also differentiate tenors and basses.

ISSN:0001-4966    

DOI:10.1121/1.381438

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP