摘要:

In 1953, Cherry found that a subject can repeat virtually all of a continuous message that is switched alternately to his left and right ears, except at certain critical rates of alternation around 3 cps. The experiments reported here investigated the effect described by Cherry. In the first experiment, the intelligibility of continuous speech was measured as a function of rate of alternation, which ranged from 1–16 cps. Two such functions were measured, one using normal speech and the other using the same speech played back at slightly increased speed. Comparison of the two functions shows that, when the playback speed of the speech was increased, the rate of alternation that gave subjects most difficulty also increased by the same factor. Therefore, the effect cannot be ascribed to any processing time, etc., that is independent of the speech, but must occur because the speech reaches each of the listener's ears in segments, as a result of which some portions of the speech wave arrive in such a form that he cannot extract the cues from them. A second experiment compared the words that were correctly repeated by subjects who heard alternated speech with the words that were identified by subjects who heard only the signal for the left ear (interrupted speech) and the words that were identified by subjects who heard only the signal for the right ear (also interrupted speech, but complementary to the left‐ear signal). It was found that the performance of subjects repeating alternated speech can be adequately described as the sum of the performances of the two groups of subjects who repeated interrupted speech, at all rates of alternation, if allowance is made for the additional context available to the alternation subjects, who heard both the left‐ear signal and the right‐ear signal, one in each ear.

ISSN:0001-4966    

DOI:10.1121/1.1919151

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

This report describes all attempt to determine the number and nature of the basic ways in which voices are perceived to differ from each other by a typical listener. In the experiment, 32 listeners described their perceptions of 16 voices by means of a semantic‐differential rating form. Analysis of variance was performed to determine the contributions of speakers, listeners, and various situational parameters to the variance of ratings on each item. Factor‐analytic techniques were employed to determine the dimensionality of the speaker effect, the listener effect, and the effect of the interaction of speakers and listeners. Four factors, labeled clarity, roughness, magnitude, and animation were found to account for an average of 88% of the variance in mean ratings given speakers on each of the 49 items. Six dimensions were found to account for the common‐factor variance in constant errors associated with listeners. Five dimensions were found to account for the common factor variance of the observed interaction of speakers and listeners.

ISSN:0001-4966    

DOI:10.1121/1.1919153

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Wave propagation in an infinite isotropic elastic plate with tractionfree faces is governed by the Rayleigh‐Lamb frequency equation. As is well‐known, an analysis of the equivalent viscoelastic problem shows that the frequency equation for an isotropic viscoelastic plate may be obtained from the Rayleigh‐Lamb equation by replacing the two independent elastic constants with complex functions of frequency. The propagation wavenumbers corresponding to modes that propagate unattenuated in an elastic plate are complex in a viscoelastic plate, the imaginary parts being attenuation constants. In this paper, an approximate method is developed for obtaining roots of the viscoelastic‐frequency equation from known roots of the Rayleigh‐Lamb equation with comparatively little additional calculation. The approximate method is applicable when the attenuation per wavelength is small. Calculations have been carried out for the lowest three longitudinal and flexural modes in plates with Poisson's ratios of 0.17 and 0.35, and curves are presented that show the contributions to the over‐all attenuation owing to dissipation associated with dilatational and shear deformations separately. As an example, the variation of attenuation with frequency in a Voigt solid has been calculated and plotted for two ratios of dilatational to shear losses. The same procedure can be used to calculate the attenuation in an isotropic viscoelastic cylinder, using the Pochhammer‐Chree equation, and numerical results are given for the longitudinal modes of a cylinder.

ISSN:0001-4966    

DOI:10.1121/1.1919155

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

When two transducers are coupled together by a sound channel such as a water‐filled steel tube and independently driven at a common frequency, dynamic control may be exerted over the acoustic impedance presented by the channel to either of the transducers. The determination of this load in the practical case, however, presents considerable experimental difficulty. For the ideal rigid‐walled channel excited by symmetrically mounted piston sources, the load impedances may be expressed in terms either of the ratio of the source velocities or of their blocked driving forces. At frequencies below those for which radial mode propagation occurs within the channel medium, the load impedances may be also related to the standing‐wave ratio of the longitudinal mode. This latter relationship seems better suited to practical measurements. Of particular interest for underwater acoustic calibration is the use of the active‐load technique to produce plane progressive waves inside a practical water‐filled steel tube.

ISSN:0001-4966    

DOI:10.1121/1.1919157

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Two basic configurations are considered in this paper: (1) a resonant cavity with a single‐input waveguide of vanishingly small cross‐sectional dimensions, in which the pressure in the resonator and the reflection coefficient in the waveguide are investigated. Particular emphasis is laid on the behavior around a resonant frequency of the cavity; (2) a cavity with an input and an output waveguide (a “filter”), in which the the transmission properties are investigated around resonance.

ISSN:0001-4966    

DOI:10.1121/1.1919159

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The problem of determining the pressure in a circular cylindrical cavity of radiusbconnected to a circular input waveguide of radiusais formulated in terms of an integral equation. Values of the reflection coefficient in the guide and of the pressure in the cavity are given in terms of the frequency and of the dimensionless ratioa/b. The problem of the cavity with an input and an output waveguide is also analyzed, and values of the transmission coefficient of this filter are obtained.

ISSN:0001-4966    

DOI:10.1121/1.1919161

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The attenuation of sound waves in mixtures of oxygen and water vapor contained in a tube has been measured at frequencies between 90 and 1200 cps. The tube was terminated at one end by a fixed reflector and at the other by a plane diaphragm producing the sound waves. The impedance of the diaphragm/gas‐column system was investigated near natural modes of the tube and analyzed by means of a circle diagram to yield the attenuation coefficient. The frequency of maximum absorption of sound was found to be a quadratic function of the water‐vapor concentration. The value of the vibrational specific heat for oxygen was found to be (0.0332+0.0015) R.

ISSN:0001-4966    

DOI:10.1121/1.1919163

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The exact solution, in infinite series form, is given to the problem of the transmission of an axially symmetric sound wave through an ideal stretched membrane in a rigid circular tube. Certain simple exact results are deduced, and the exact equations for the resonance and antiresonance frequencies are considered. It is shown that, for an incident plane wave, above a certain frequency there are no exact resonances or antiresonances. Below this frequency, the resonances and antiresonances differ from those predicted by approximate methods, and, contrary to the simple results, their frequencies depend on the density of the medium surrounding the membrane. The same analysis, which involves the inversion of an infinite matrix, applies also to the parallel‐plate guide and to transmission through a thin elastic plate. Numerical results are given for a particular case.

ISSN:0001-4966    

DOI:10.1121/1.1919165

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Resonance damping for a vibrating plate is investigated both according to the exact equations of dynamical viscoelasticity and the classical thin‐plate equations derived in mechanics of materials. The plate is assumed as isotropic and homogeneous and no shear‐ or rotatory‐inertia corrections have been included in the thin‐plate approximations. Two types of materials are investigated that correspond to real and complex values of the bulk modulus. For each case, the complex shear modulus is μ(1+ig) and values ofgup to 0.10 were used in the calculations. The two theories are in excellent agreement in a range of wavelengths as low as about ten times the thickness. It is found that thin‐plate theory evaluates the damping more accurately than it does the static rigidity.

ISSN:0001-4966    

DOI:10.1121/1.1919167

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

In this paper, a treatment for determining the eigenfunctions and eigenvalues for the vibration of a circular membrane with fixed boundary and density varying as exp[− εγ2] is made by the method of perturbation, and the expressions for perturbed eigenvalues and eigenfunctions are obtained up to second‐order terms. The first‐order perturbed term of the eigenvalue is effected by numerical integration.

ISSN:0001-4966    

DOI:10.1121/1.1919169

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP