摘要:

This paper is concerned with the dynamical behavior of the cochlea. It is assumed that a length of the basilar membrane which is equal to its width at each position vibrates as a unit, and that the forces exerted upon it by adjacent units are negligible compared to that exerted by the difference in pressure in the scala vestibuli and scala tympani. The boundary conditions at the stapes end is simply that the pressure difference in the two canals is equal toP0any desired pressure difference. However, at the helicotrema the pressure difference must be equal to that between the two ends of the capillary opening at the helicotrema.Then from the fundamental hydrodynamical equations and the experimental constants obtained by Békésy it is shown that the speed of sound through the liquid of the inner ear may be considered infinite compared to the speed of the wave along the basilar membrane. In other words, the liquid may be considered incompressible so that the rate of liquid displacement at the oval window is equal to that at the round window, and is also equal to that produced by flexure of the basilar for frequencies above 200 cps. Below this frequency some of the liquid goes back and forth through the helicotrema.With these assumptions, the following quantities were calculated from the fundamental dynamical equations and found to be in good agreement with the experimental results of Békésy; (a) displacement amplitudes and phases of the basilar membrane at different distances from the stapes and for different frequencies, (b) time for wave to travel from stapes to various distances from stapes, and (c) volume displacement, at various frequencies, per dyne difference of pressure at oval window and that at round window.

ISSN:0001-4966    

DOI:10.1121/1.1906813

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

The loudness and threshold of an interrupted white noise (of constant sound‐time fraction) was studied over a wide range of interruption frequencies. White noise has the useful property that, when interrupted, no spectral changes result in the white noise spectrum (in the frequency range passed by a dynamic earphone). Both at the threshold and at equal‐loudness, less energy is needed for an interrupted noise than for a continuous noise. In many cases, an interrupted noise (sound‐time fraction of 0.45) sounds louder than a continuous noise of the same burst amplitude (but of greater energy). There is a broad minimum, in the intensity required at equal loudness, for interruption rates between 2–10 per second. A conceptual formulation to encompass the results is presented.

ISSN:0001-4966    

DOI:10.1121/1.1906814

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

Thresholds for the detection of a decrement in noise intensity between repeated bursts of noise were determined as a function of the duration of the interval between successive bursts. The results indicate acritical duration(55 milliseconds) between successive noise bursts: (1) above which, the differential threshold is constant and independent of the interval between successive bursts and (2) below which, the differential threshold increases proportionately as the interval between successive bursts decreases. Since an equivalent critical interval has previously been obtained by several different independent measures of auditory persistence, the observed deterioration of differential sensitivity is interpreted in terms of the overlap or addition of auditory persistence with the direct effects of stimulation.

ISSN:0001-4966    

DOI:10.1121/1.1906815

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

Scales of loudness for complex sounds have usually been obtained by determining the equal‐loudness relation between the complex sound under investigation and a sound for which a scale of loudness is already available, e.g., a pure tone of 1000 cps. It is possible, however, to determine scales of loudness for complex sounds without appeal to pure tones or without extrapolation from pure‐tone data. This was done in the present experiment. Loudness measurements were carried out by several independent procedures for a 1000‐ cycle tone and for white noise. The agreement among the different procedures indicates satisfactory internal consistency among the several methods of determining loudness scales. A suggested scale of loudness for white noise, based upon all available data, is presented.

ISSN:0001-4966    

DOI:10.1121/1.1906816

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

This paper presents data for changes of pitch with intensity for 18 ears, for frequencies from 125 cps to 8000 cps, and for intensities up to a loudness level of approximately 100 db. There are wide individual differences, but most observers show very small changes (less than 2 percent) of pitch with intensity. In general, as intensity is increased, pitch falls at low frequencies and rises at high frequencies. Two different methods of measuring pitch‐intensity changes showed no significant difference.

ISSN:0001-4966    

DOI:10.1121/1.1906817

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

Fifty‐four naive observers were asked to report whether they could hear a difference between two successive tones which differed only in respect to which ear was leading in phase angle. They were not given specific suggestions to listen for a particular effect, but were later asked what they had heard. Two intensities, eight frequencies, and seven phase leads were used. The major conclusions from the results are: (1) All observers heard differences due to phase and identified the differences as localization, although for most the localization was in terms of which ear was stimulated rather than in terms of apparent localization of a sound source. (2) Pitch and loudness differences also occurred, but cannot be explained on the assumption that only one ear was effectively stimulated. (3) Measures of phase‐difference thresholds, upper frequency limits, and time‐difference thresholds show approximately the same results as are obtained with other methods.

ISSN:0001-4966    

DOI:10.1121/1.1906818

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

This study is aimed primarily at evaluating the utility of axis‐crossing detectors in tracking speech formants. Detectors of the usual type are found subject to an error, fundamental in nature. To remove this source of error speech is modulated up in frequency as a single sideband before limiting and detecting processes are applied. Experimental results with this carrier type of detector on a small number of speech samples are presented, and compared with spectrograms.Conclusions are that the average axis‐crossing rates cannot be trusted in general to follow specific formants, whether the speech is normal or differentiated. But when the formants are sufficiently localized by frequency selectivity, prospects of tracking the lower formants look promising.

ISSN:0001-4966    

DOI:10.1121/1.1906819

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

The points of zero crossing and the points of zero slope of the oscillograms of speech sounds are considered to contain the essential information for intelligibility. The intervals between zero crossings θ0, and the intervals between zero slopes θm, are plotted as points in rectangular coordinates. The ordinate of the dot is a function of θ (θ0or θm), and the abscissa is a function of the time of occurrencetof the particular θ. The resulting intervalgram gives a half‐tone picture (consisting of dots) of speech sounds. The patterns may be proportioned to show either a detailed or general representation of the variation of the interval distribution. One type of pattern portrayed at the speech rate on a cathode‐ray oscilloscope with a screen of long persistence has been found quite similar in certain respects to the patterns obtained using the sound spectrograph as described in the bookVisible Speechby Potter, Kopp, and Green. The equipment involved in obtaining the intervalgram, however, is much simpler.

ISSN:0001-4966    

DOI:10.1121/1.1906820

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

The use of the conventional analog for diaphragms in equivalent circuits often causes serious difficulties. The action of a diaphragm is shown to be analogous to that of a system of ideal transformers, each corresponding to an area of the diaphragm. The ancillary concept of “acoustical ground” analogy is introduced to facilitate synthesis of equivalent electrical circuits. The analysis includes equivalent circuit representations of a piston diaphragm, multiple diaphragms, diaphragms with subdivided sides, and articulated diaphragms, etc., together with examples. Simultaneous use of the transformer analogy of diaphragms and the transformer analogy of transducer couplings is treated in the Appendix.

ISSN:0001-4966    

DOI:10.1121/1.1906821

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

This paper describes a pulse technique which makes possible a free‐field reciprocity calibration of a microphone indoors, without recourse to an anechoic chamber. The method is limited to frequencies above the middle audio range by consideration of the room size and pulse spectrum. An experimental calibration of a microphone is included, and waveforms are presented which demonstrate the validity of the method.

ISSN:0001-4966    

DOI:10.1121/1.1906822

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP