摘要:

Round‐window displacements were recorded by means of time‐averaged holography in live cats and in fresh animal cadaver specimens. Considerable technical difficulties had to be overcome first, before such recordings became feasible. In the majority of cases, the displacement pattern was complex, even at low frequencies, with the maximum displacement occurring in the anterio‐superior region. Between‐animal variations were relatively large. From the reconstructions, volume displacements and eventually volume velocities were calculated for given frequencies. Since the sound pressures had been directly applied to the stapes footplate, the volume velocities for given sound‐pressure levels (SPLs) could be converted into inner‐ear impedance values, the assumption being that, for a given situation, volume displacements of the round window should equal those of the oval window. Inner‐ear impedances were in the low megohm range; in this respect the results confirm those of an earlier study from this laboratory. However, while in cadaver specimens the results were reasonably uniform, in live animals impedance appeared to increase with exposure to high SPLs. This increase in impedance appears to exert a protective function for the inner ear. Experiments to explore this latter function in more detail are being planned.

ISSN:0001-4966    

DOI:10.1121/1.1912801

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A narrow band of noise (50 Hz wide centered at 250 Hz) was passed through a phase‐shifting network and was then used as both masker and signal. The phase shifter permitted control over the phase angle α at which the signal and the masker were added. The masker was continuously present and was in‐phase interaurally N0); the signal could be presented in‐phase interaurally (S0) or 180° out‐of‐phase (Sπ). Detection data were taken for N0‐S0, α = 0° (increments) and α = 180° (decrements), and both detection and lateralization data were taken for N0‐Sπ for several values of α. A single‐interval psychophysical method was used throughout. For all subjects for all values of α, the masking‐level differences (MLDs) were positive and substantial. In the N0‐Sπ conditions, two cues were available to the subject for all values of α except 0° and 90°—an interaural phase (time) difference and an interaural difference in level. Between α = 0° and α = 90 °, the two cues are consonant, but between α = 90° and α = 180°, the two cues are in opposition, i.e., one cue indicates that the sound source is to one side of the median plane while the other cue indicates that it is to the other side. Some subjects were more sensitive to one of these cues, and other subjects were more sensitive to the other cue; this fact was apparent in both their detection and their lateralization data. For each subject there was a value of α between about 120° and 170° at which detection performance was good while lateralization was nearly impossible.

ISSN:0001-4966    

DOI:10.1121/1.1912802

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

This paper presents a quantitative functional model, called the correlation model, to be used for interpreting empirical results on binaural masking level differences (BMLDs), which are obtained experiments on the detection of sinusoidal signals embedded in binaural noise. The receiver is presumed to behave as if it computes a statistical decision variable equivalent to a linear combination of three quantities, the energy levels at the channels deriving from the two ears and the interchannel cross correlation, where the coefficients are dependent on the interaural noise cross correlation and the interaural amplitude ratio for noise but are completely independent of signal parameters. Additive internal noise is assumed. Equations for BMLDs are derived with the restriction of equal noise levels at the two ears. Predictions derived from the model are compared with empirical results from several studies. These show BMLDs for antiphasic, homophasic, and monoaural input configurations at different frequencies of tonal signal, and BMLDs for varying interaural correlations of signal and of noise, where the noise correlation is statistical or deterministic. Similarities and differences between the correlation model and another model, the equalization cancellation model, are discussed in detail.

ISSN:0001-4966    

DOI:10.1121/1.1912803

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A form of the discrete‐moment hypothesis of Stroud, usually studied in relation to vision, is tested in audition by means of the masking of a click by a preceding or a following noise burst. Threshold masking and temporal psychometric functions suggest that, if a discrete‐moment mechanism were operating, the time between successive moment onsets would be as short as 3 msec. Through a second‐choice procedure, we attempted to distinguish between a continuous moment or signal detection class of hypotheses and the discrete‐moment hypothesis. The results for one subject disagree with the prediction of the discrete‐moment hypothesis.

ISSN:0001-4966    

DOI:10.1121/1.1912804

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The study concerns units of the cochlear nucleus of anesthetized Mongolian gerbils. The incremental stimuli consisted of short tone bursts at the units' CF (characteristic frequency) superimposed on 250‐msec pedestals of the same sound frequency and phase. The response firing rates were determined from PST (poststimulus time) histograms. In response to the pedestals, the maximum firing rate occurred at the tone onset and decayed subsequently to a steady state. The response to intensity increments was studied as a function of time delay from the pedestal onset to the increment onset. The incremental firing rate either remained constant or increased with the time delay, which means that the ratio between the incremental and pedestal firing rates always increased. The effect may be related to the psychophysical finding that intensity increments are the most difficult to detect when they occur at the pedestal onset.

ISSN:0001-4966    

DOI:10.1121/1.1912805

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Lateralization of brief clicks was studied while the frequency content of the clicks was altered by filtering. The subject was asked to discriminate a centered image, a pair of identical clicks that arrived simultaneously at the two headphones, from a displaced image, a pair of identical clicks in which the click to the left ear was slightly delayed. The discrimination of the lateral position deteriorated as the clicks were high‐pass filtered beyond 1500 Hz and was largely unaffected by low‐pass filtering. Masking with high‐pass and low‐pass noise showed that low‐pass noise severely disrupted the lateralization of the high‐pass clicks, but the high‐pass noise produced no disruption of the lateralization of the low‐pass clicks. Our results suggest that the discrimination of lateral position depends largely on the low‐frequency content of the click and thus, presumably, on the apical end of cochlear partition.

ISSN:0001-4966    

DOI:10.1121/1.1912806

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A subjective evaluation of the effects of smoothing and quantization of the parameters for formant‐coded voiced speech has been carried out. Thresholds were obtained for the degree of smoothing or quantization of specified parameters associated with a just noticeable degradation of all‐voiced sentence material. Average quantization threshold levels obtained were: pitch period, 3.9 bits; first formant, 2.7 bits; second formant, 3.1 bits. The average of low‐pass filter bandwidth thresholds for the simultaneous smoothing of formants was 7.6 Hz per formant; for pitch‐period data the low‐pass filter bandwidth threshold was 3.9 Hz. With simultaneous low‐pass filtering and quantization, the estimated over‐all bit rate for the coded parameters of all‐voiced speech was approximately 200 bits/sec.

ISSN:0001-4966    

DOI:10.1121/1.1912807

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Gassy and degassed aqueous solutions of DNA were treated ultrasonically while monitoring the field for discrete cavitation events. At irradiation intensities greater than about 500 W/cm2, transient cavitation is shown to be responsible for the observed reduction in molecular weight. At intensities of 200 to 288 W/cm2, degradation of DNA was observed which did not depend upon transient cavitation.

ISSN:0001-4966    

DOI:10.1121/1.1912808

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

An amoeba,Hartmannella castellanii,which possesses many features typical of higher‐order animal cells, was irradiated with 1‐MHz ultrasound while suspended in ordinary growth medium and in one with increased viscosity. The ultrasonically produced cavitation was monitored and a strong correlation is found between the number of discrete cavitation events occurring and the decrease in cell numbers, on irradiating at 515 W/cm2for 10 min. The growth of treated cells was also examined.

ISSN:0001-4966    

DOI:10.1121/1.1912809

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

It is argued that the apparent covariance of cochlear microphonic (CM) and behavioral sensitivity is a result of the common dependence of both upon the middle‐ear transmission characteristics and not an indication of the causal role of CM in hearing.

ISSN:0001-4966    

DOI:10.1121/1.1912810

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP