摘要:

All organizations perform evaluations of their own purposes and effectiveness. The efforts of the Acoustical Society of America to this end during the past three years have included special studies by the Ad Hoc Committee on the Effectiveness of the Society. Recommendations of this Committee have resulted in a revitalization of activities in standards, formulization of a committee and programs in environmental acoustics, and the conduct of a Conference on Acoustics and Societal Problems. The Conference was made possible through a grant from the National Science Foundation and is reported upon here. The Conference, which was held at the Arden House 18–21 June 1973 with 52 participants in attendance, addressed the definition of problems of society at large which are of particular concern to the Acoustical Society of America as a corporate body, and to its members. The Conference established several vital elements—ranging from improved communications, through delineation of unsolved basic and applied research problems, to needs for strong leadership by the Acoustical Society of America—if an increased rate of progress is to be achieved during the next decade in areas dependent upon acoustics. A summary of these elements is set forth in this report.

ISSN:0001-4966    

DOI:10.1121/1.1913563

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The purpose of this experiment was to determine whether temporal effects on frequency discrimination were the same for persons with sensorineural loss and for persons with normal sensitivity. Estimates of the difference limen for frequency (DLF) were obtained for signals of 50‐ and 500‐msec durations, for standard frequencies of 0.5, 1.5, and 3.0 kHz. In most of the conditions, the temporal effects on frequency discrimination were similar for hearing‐impaired and normal‐hearing subjects. Speech discrimination of the five hearing‐impaired subjects also was measured. The highest rank‐order correlation (rs= 1.0) was found between DLF at 3.0 kHz and vowel‐ and consonant‐discrimination scores.

ISSN:0001-4966    

DOI:10.1121/1.1913550

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The characteristics of the short‐term poststimulatory depression (hysteresis) have been studied by recording cochlear microphonics (CM) with differential electrodes at several locations along the guinea‐pig cochlea. The depression appears, with high‐intensity tones, in regions where the vibratory amplitude of the cochlear partition is the largest. It is accompanied by a negative summating potential (SP) whose time course follows exactly the variation of the CM amplitude and in particular outlasts the presentation of the stimulus. At the same time, complex hydrodynamic effects are observed by microscopy. They result in a flow of perilymph from scala vestibuli toward the vestibular spaces, and the membranes of the cochlear partition are displaced in an extreme position. These displacements might provide a protective mechanism against acoustic trauma.

ISSN:0001-4966    

DOI:10.1121/1.1913560

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Informational constraints were encoded within individual pulses of multivariate auditory displays. Sensitivity for the constraints was determined by forced‐choice discrimination tests. With a single informational constraint imposed upon a combination of display variables, discrimination is impaired as additional display variables contribute to the constraint. With multiple informational constraints, discrimination improves with the number of constraints, and thereby improves with the number of controlled display variables. The latter result is consistent with the identification of individual dimensions of multivariate auditory displays.

ISSN:0001-4966    

DOI:10.1121/1.1913569

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A speech analysis‐synthesis system was used to manipulate variance of fundamental frequency and a mechanical rate changer was used to manipulate speech rate. The synthesized and altered voices were tested for realism. Synthesized voices were mistaken for normal 50% to 58% of the time and rate‐changed voices were mistaken for normal 78% of the time. Additional studies were conducted to test the effects of these acoustical manipulations on the adjective ratings judges made of speakers. Variance of intonation was increased and decreased by 50% for eight speakers. There was a significant trend for increased intonation to cause voices to be rated more “benevolent” by judges and decreased intonation to cause them to be rated less “benevolent.” In two additional studies, rate was decreased and increased by varying amounts. Slowing the voices caused them to be rated less “competent.” Speeding the voices caused them to be rated less “benevolent.” Results were more consistent over speakers for rate manipulations than for intonation manipulations.

ISSN:0001-4966    

DOI:10.1121/1.1913571

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The following analysis develops the equation for the scattered acoustic power and spectral broadening of a plane acoustic pulse propagating through atmospheric turbulence that is moving with a uniform wind transverse to the beam. Assuming weak single scattering, the resulting propagation broadening is proportional to the wind velocity divided by the outer scale of turbulence and is independent of the strength of turbulence and total propagation range. Further, the broadening for a medium with variable outer scale and wind shear (e.g., a vertical propagation path) is determined primarily by the highest ratio of transverse wind to outer scale encountered by the pulse.

ISSN:0001-4966    

DOI:10.1121/1.1913572

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

An integral‐equation approach is utilized in numerically determining dispersion relations for guided surface waves on an elastic half space. The surface waveguide problem is first cast as a partial‐differential‐equation boundary‐value problem whereupon an application of the bilateral Laplace transform enables transformed displacement to be determined as a function of transformed stress. By inverting the transformed displacement directly and incorporating the boundary conditions, one can obtain an integral‐equation formulation of the boundary‐value problem which is analyzed numerically to yield dispersion relations. The problem which is considered assumes that an elastic half space is in contact with two rigid smooth barriers. A waveguide is formed by arranging the barriers so that a strip on the surface of uniform width is traction free. It is demonstrated that a valid simplification in waveguide problems is that body‐wave disturbances, localized in the vicinity of each edge of the guide, have negligible effect on the reflection of surface waves at the opposite edge of the guide.

ISSN:0001-4966    

DOI:10.1121/1.1913573

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

An absorber theory of acoustical radiation is developed by analogy to Wheeler‐Feynman electrodynamics. Using a method due to Feynman the acoustic index of refraction for a system of soft spherical scatterers is calculated. The effects of these scatterers on an acoustic source are summed to obtain the usual radiation reaction.

ISSN:0001-4966    

DOI:10.1121/1.1913574

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The mathematical formalism for obtaining dispersion relations for acoustic waves in plates of arbitrary anisotropy is outlined, and dispersion curves for propagation in a (001)‐cut cubic plate are presented. These results are compared to the uncoupledSVandPmodes which, in turn, are related to the slowness curves for bulk waves. This approach provides an explanation for the behavior of the computed dispersion curves, and it also provides a means of approximating plate wave dispersion curves from the behavior of the slowness curves. The relationship of plate waves to surface waves is also explored for directions in which pseudosurface waves are known to propagate.

ISSN:0001-4966    

DOI:10.1121/1.1913575

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The potential method is extended to treat the reflection and scattering of acoustic waves by rough surfaces. The resulting expression for the scattered pressure contains terms which can be identified as the singly and multiply scattered field components. In addition, a boundary condition that approximately accounts for shadowing is used. Only the singly scattered field term is specialized to a form that is convenient for reflected or scattered pressure and intensity calculations. Finally, the assumption of a randomly rough surface is introduced and very general results concerning the coherent and total scattered fields are obtained.

ISSN:0001-4966    

DOI:10.1121/1.1913576

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP