摘要:

Attention is drawn to the errors that might arise in allowing for the direct energy in a receiving enclosure. Formulas are developed for the mean direct‐energy density throughout the room and also for its dependence on the distance from the radiating wall. Comparisons with the reverberant levels in the room are made for various assumed distributions of wall absorption.

ISSN:0001-4966    

DOI:10.1121/1.1910039

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Microphonic potentials were recorded from the cochleas of guinea pigs and chinchillas. It was observed that with intense pure‐tone stimuli, subharmonic potentials could be detected in the microphonic. These potentials possess high threshold (between 110 and 130 dB SPL), above which they immediately assume magnitudes that are commensurate with that of the fundamental. Increase in stimulus intensity above the threshold results in some increase in the magnitude of the undertones, but saturation and rapid decline follow within a 10‐ 15‐dB range. The most frequent subharmonic appears at one half the driving frequency, but the quarter‐frequency component is also common.

ISSN:0001-4966    

DOI:10.1121/1.1910063

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

The present investigations were conducted to determine and describe some of the acoustic parameters of central masking. Shifts in threshold were observed during the following monotic and dichotic conditions: (1) pulsed pulsed, in which both test signal and masker were pulsed simultaneously; (2) pulsed continuous, in which the test tone was pulsed but the masker was continuous; and (3) continuous‐continuous, in which both test tone and masker were steady. Test signals of 250, 1000, and 4000 cps were used. It was found that the degree of threshold shift resulting from central masking factors was dependent on the temporal presentation of the test signal and masker (whether pulsed or steady). Threshold shifts due to central masking increased with frequency and were related to the spectrum level of the masker. The largest shifts in threshold were found for a 4000 cps test signal when the masker was a pure tone close in frequency. In these instances, lateralization of the test signal toward the midline was observed as the threshold shift increased and, at times, subjects were unable to distinguish between the test tone and pure‐tone masker. Although the results can be explained on the basis of central masking factors, the manner in which the subjects traced their thresholds during the condition where both test signal and masker tone were continuous suggested that all observed shifts in threshold may not be clue to masking alone.

ISSN:0001-4966    

DOI:10.1121/1.1910028

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

When a strong signal is presented monaurally, listeners can easily lateralize the sound. However, if noise is added to both ears, there may be uncertainty as to which ear received the signal. This uncertainty was measured over a range of signal energies with perfectly correlated noise (N0) and with uncorrelated noise (NU). In the main experiment, the monaural signal occurred on each trial, and this signal was presented to either the right or the left ear by random determination during the single observation interval. Listeners responded “right” or “left.” Measures of signal detection were also secured with the monaural signal under release from masking (N0) and without such release (NU). With uncorrelated noise (NU), the listener requires only slightly greater signal energy (1–2 dB) in order to lateralize as well as he can detect. With correlated noise (N0), the psychometric function for lateralization is not only displaced considerably toward higher signal energies, relative to those required for detection, but the slope of the function for lateralization is smaller than that for detection. When a monaural signal is easily detected in uncorrelated noise, it is also easily lateralized. However, when the signal is strong enough to be readily detected with correlated noise, it is still poorly lateralized.

ISSN:0001-4966    

DOI:10.1121/1.1910041

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Three experiments are reported that employed 78 normally hearing college students who demonstrated an ability to concentrate on an interrupted white noise that alternated with a tonal burst. The purpose of these experiments was to investigate the effects of the duration of the white noise and the frequency of the tonal burst on the perception of continuity under monaural and dichotic presentation. The effect of the number of noise pulses in the stimulus interval was also investigated. The results showed that under monaural presentation the perception of continuity was affected by both the duration of the noise and the frequency of the tone. Only the duration variable was significant under dichotic presentation. The number of noise pulses in the stimulus interval significantly affected the perception of continuity.

ISSN:0001-4966    

DOI:10.1121/1.1910059

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

In the toadXenopus laevis, the lateral line system may be considered as a single organ, containing about 30 000 hair cells, which is used to detect moving objects. It is organized in groups of neuromasts, called stitches, which are directionally sensitive to water velocity. Each stitch is innervated by two large (∼8 μ) myelinated fibers. Electrophysiological recordings made from the nerve to a piece of skinin vitroshow that these two fibers are spontaneously active and are sensitive to water velocities in opposite directions. The spontaneous activity in one fiber may have a slight positive correlation with the spontaneous activity in the other. This indicates that the origin of the spontaneous activity should not be Brownian motion of the cupula. Its origin is probably in the portion of the nerve between the hair cells and the start of myelination. Interval histograms of spontaneous activity show an exponential tail for long intervals and few small intervals. There is a characteristic absence of intervals less than about 10 msec. Evoked responses are repetitive, with rate, number of spikes, and latency, dependent on stimulus intensity. These results indicate that both place and pulse position coding could be used to convey the information necessary for the perception proper to this organ.

ISSN:0001-4966    

DOI:10.1121/1.1910060

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

This paper reports differential sensitivity for pitch memory of pure tones as frequencies from 0.125 to 2 kcps are progressively raised above white noise adjusted to a 50% masking effect at the 45‐dB sensation level of the tone. The Weber fraction (DF/F) improves with some negative acceleration through 2 kcps both in favorable and in unfavorable masking levels, but below about 0.5 kcps the sensitivity progressively deteriorates. The Weber fraction is related linearly to loudness, the loudness of tones in noise being specified by balancing to a 1‐kcps tone in quiet. However, tones in noise exhibit poorer Weber fractions than tones at the same loudness but with no mask. Thus, the noise introduces a brake on sensitivity not only by loudness reduction but by an additional mechanism. The number of distinguishable pitches between 0.125–2 kcps is reduced from 548 for tones in quiet at 45 dB sensation level, to only 170 for tones in noise at a very unfavorable (signal‐to‐noise) S/N ratio (tones 5 db over the 50% masking point.)

ISSN:0001-4966    

DOI:10.1121/1.1910061

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

In the normal‐hearing subject, a sensation of unpleasant loudness is invariably associated with intensities of the order of 100 dB within the frequency range 500–4000 cps. This is referred to as the loudness‐discomfort level (LDL). The intensity distribution of LDL has been established in a large group of subjects with unilateral end‐organ deafness, in all of whom the presence of loudness recruitment had been verified by means of the alternate binaural loudness balancing procedure. In these, the distribution was similar to that of a normal‐hearing group. By contrast, the LDL's of subjects with conductive or nerve‐fibre deafness exceeded the maximum available audiometer intensity of 120 db. The test, therefore, is of particular value in establishing the presence or absence of loudness recruitment in bilateral deafness. These findings suggest a physiological limit of loudness perception, the theoretical implications of which are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1910062

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

A model of cochlear mechanics is specified by a set of differential equations that relate pressures and displacements in the inner ear. The assumptions implicit in the equations are considered in this paper. The equations are solved by a straightforward difference‐equation approximation on a digital computer. An equivalent electronic circuit was constructed in order to examine certain of the characteristics of the model. The response of the model is compared to physical data from a number of experiments.

ISSN:0001-4966    

DOI:10.1121/1.1910064

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

This paper reports the results of further experiments on the binaural unmasking of tones masked by broadband Gaussian noise and further theoretical work on the EC model of binaural unmasking. Data are presented on binaural unmasking for interaural time delays and/or phase shifts in the noise, and for statistically independent noise, at a variety of tone frequencies. Many aspects of these data cannot be interpreted by the preliminary version of the model, and consideration is given to some possible revisions of the model.

ISSN:0001-4966    

DOI:10.1121/1.1910065

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP