摘要:

Numerical predictions for the reflection of plane sound waves from a pressure‐release sinusoidal surface of large slope are compared with experimental data. The approach introduced recently by Uretsky [J. Acoust. Soc. Am.35, 1293–1294 (1963)] for the calculation of reflection coefficients was adopted with some modification owing to the geometrical parameters of the surface and the frequency of the incident sound. The geometry of the surface and the experiment were such that theory could be tested with three orders of the grating spectra.

ISSN:0001-4966    

DOI:10.1121/1.1910006

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Normal‐mode theory is applied to the problem of finding the variation of acoustic intensity with range in shallow water of variable depth. A solution of the wave equation is obtained by neglecting the coupling of normal modes produced by the horizontal variation of depth. Relatively simple formulas for the intensity as a function of range are obtained in the case of isovelocity water by averaging the expression for intensity over source and receiver positions and replacing a Summation over all the allowed modes by an integration at intermediate ranges. At long ranges, only the first mode is effective and a modified cylindrical spreading law is obtained.

ISSN:0001-4966    

DOI:10.1121/1.1910007

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Ambient noise under short‐fast sea ice in midwinter is generated at the surface of the ice by wind action as well as by mechanical cracking caused by declining air temperatures. An attempt has been made to relate field measurements of underwater noise to the sources of the noise by means of a geometrical model of the environment. The statistical properties and the spectra of the under ice noise can be related to the surface density and the waveform of the source pressure pulses by means of the model.

ISSN:0001-4966    

DOI:10.1121/1.1910008

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Modifications to a Rudmose ARJ‐4 are described that permit thresholds to be presented as a binary decimal code on punched tape suitable for processing by a digital computer.

ISSN:0001-4966    

DOI:10.1121/1.1910009

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Data are presented relating to the thresholds of three different samples of normally hearing subjects, which indicate that the British standard and recommended ISO reference zero for audiometers is insufficiently stringent by approximately 3 dB over the frequency range 0.5 to 6 kcps. Determinations of threshold, made with the same audiometer and the same earphone placement, by a conventional manual method and by a self‐recording method showed the latter to give an average threshold more sensitive than the manual usage gave by less than 1 dB. The inaccurate nature of current procedures for audiometer calibration employing a single subjective correction for all receivers of a particular pattern is stressed.

ISSN:0001-4966    

DOI:10.1121/1.1910010

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Two independent series of measurements of normal auditory threshold have been carried out with fixed‐frequency self‐recording audiometers. The results are in close‐agreement with each other, but yield threshold levels that are distinctly more acute than the International Stanford reference levels (ISO‐R,389; 1964), the exact difference varying somewhat according to different methods of application of the standard to TDH‐39; MX‐41‐AR earphones. Possible reasons for the more‐acute thresholds are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1910011

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Recent subjective threshold calibrations of a range of audiometric earphones permit direct comparison of their equivalent threshold sound‐pressure levels on various artificial ears and couplers. Values of equivalent normal threshold sound‐pressure level, compatible with ISO Recommendation R389, are given for the TDH39 MX41‐AR earphones on an NBS type 9A coupler.

ISSN:0001-4966    

DOI:10.1121/1.1910012

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

The possible advantages of including measurements of reaction time in speech‐intelligibility tests are discussed. Such procedures are likely to provide independent measures of the performance of speech‐communication systems and to increase the sensitivity of conventional intelligibility tests. A preliminary experiment employing an automated version of a multiple‐choice test is used to illustrate this approach.

ISSN:0001-4966    

DOI:10.1121/1.1910013

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Intelligibility scores were obtained from 240 listeners for monosyllabic words. In Expt. 1, noise was introduced at the lowest end of the spectrum and, in Expt. 2, at the highest. Throughout the listening task, speech was presented through one of four “equally contributing intelligibility bands” (quarter‐bands) of the speech spectrum: 300–760, 760–1450, 1450–2550, and 2550–7000 cps. Intelligibility in the channels (quarter‐bands) at the opposite ends from the noise was superior in the experimental condition to that in the control, the control being characterized by no introduction of noise. Thus, effects similar to previously reported studies of release from masking were evident.

ISSN:0001-4966    

DOI:10.1121/1.1910014

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

A general method for the study of elastic‐ware propagation in anisotropic media is applied to the case of trigonal symmetry. A section of velocity surface for calcite is given. For elastic waves propagated in anisotropic media, the energy flux deviates from the direction of the wave normal. This prediction has been verified in the case of calcite. An optical method is used to observe the deviation of the quasilongitudinal ray from the wave normal.

ISSN:0001-4966    

DOI:10.1121/1.1910015

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP