摘要:

Performance of infants in a speech‐sound discrimination task (/ba/ vs /da/) was measured at three stimulus intensity levels (50, 60, and 70 dB SPL) using the operant head‐turn procedure. The procedure was modified so that data could be treated as though from a single‐interval (yes–no) procedure, as is commonly done, as well as if from a sustained attention (vigilance) task. Discrimination performance changed significantly with increase in intensity, suggesting caution in the interpretation of results from infant discrimination studies in which only single stimulus intensity levels within this range are used. The assumptions made about the underlying methodological model did not change the performance–intensity relationships. However, infants demonstrated response decrement, typical of vigilance tasks, which supports the notion that the head‐turn procedure is represented best by the vigilance model. Analysis then was done according to a method designed for tasks with undefined observation intervals [C. S. Watson and T. L. Nichols, J. Acoust. Soc. Am.59, 655–668 (1976)]. Results reveal that, while group data are reasonably well represented across levels of difficulty by the fixed‐interval model, there is a variation in performance as a function of time following trial onset that could lead to underestimation of performance in some cases.

ISSN:0001-4966    

DOI:10.1121/1.394757

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

The purpose of this experiment was to evaluate the utilization of short‐term spectral cues for recognition of initial plosive consonants (/b,d,g/) by normal‐hearing and by hearing‐impaired listeners differing in audiometric configuration. Recognition scores were obtained for these consonants paired with three vowels (/a,i,u/) while systematically reducing the duration (300 to 10 ms) of the synthetic consonant–vowel syllables. Results from 10 normal‐hearing and 15 hearing‐impaired listeners suggest that audiometric configuration interacts in a complex manner with the identification of short‐duration stimuli. For consonants paired with the vowels /a/ and /u/, performance deteriorated as the slope of the audiometric configuration increased. The one exception to this result was a subject who had significantly elevated pure‐tone thresholds relative to the other hearing‐impaired subjects. Despite the changes in the shape of the onset spectral cues imposed by hearing loss, with increasing duration, consonant recognition in the /a/ and /u/ context for most hearing‐impaired subjects eventually approached that of the normal‐hearing listeners. In contrast, scores for consonants paired with /i/ were poor for a majority of hearing‐impaired listeners for stimuli of all durations.

ISSN:0001-4966    

DOI:10.1121/1.394758

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

Single frequency measurements are obtained for the driving point admittance of a violin at three positions on the top of the bridge at directions parallel and normal to the top plate. Companion measurements of transfer admittance are taken from the top of the bridge to the body of the violin at the bridge feet. Phase measurements of the transfer admittance yield the phase relationship between the feet that indicates parallel or rocking motion of the bridge in its plane. These data are compared with data from other sources. The mechanical power input to the body of the instrument is calculated for an equivalent bow friction force.

ISSN:0001-4966    

DOI:10.1121/1.394759

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

The use of a multimicrophone acoustic intensity probe is investigated for the measurement of the acoustic velocity power spectrum. The conventional formulation [J. Acoust. Soc. Am.73, 1047–1053 (1983)] for this measurement is found to be sensitive to measurement errors. Three alternative formulations of the velocity estimate are developed that are less sensitive to random error. The various formulations are implemented into a four‐microphone probe for measurement of the three velocity components. Experiments in the nearfield of a piston and a periodically stiffened plate verify the predicted relative advantages of the various estimators.

ISSN:0001-4966    

DOI:10.1121/1.394760

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

An electrically conducting fluid in a magnetic field generates forces as a result of the application of an electric current in the fluid, and a wave motion in the fluid generates an electromotive force. This effect has been applied to an underwater acoustic transducer: liquid state electromagnetic transducer. For the two acoustic ports and the electrical port, three‐port equations have been presented whose coefficients are functions of such physical parameters as the duct size, fluid conductance, wave speed in the duct, and magnetic flux density. In this research, to examine the analytical model, salt water was used in a square duct of anodized aluminum, which has a pair of facing copper electrodes on the inside walls of the duct. A magnetic field was applied externally by an electromagnet. A series of measurements to evaluate every coefficient of the three‐port equations was performed. Good experimental support for the model was obtained.

ISSN:0001-4966    

DOI:10.1121/1.394761

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

A plasma loudspeaker is a transducer that produces sound by means of an ionized gas channel rather than the voice coil of a conventional loudspeaker. Plasma loudspeakers characteristically have a flat frequency response at the higher acoustic frequencies because of their ‘‘massless’’ membrane; however, their low‐frequency response is limited. In this article, a comprehensive model for the electrical and thermodynamic operation of the electrical discharge is presented that explains the frequency‐dependent behavior of the discharge’s electrical impedance and acoustic response. The characteristic acoustic frequency response is shown to result from a spatial variation of the temperature relaxation time throughout the plasma channel due to the temperature dependence of that time constant. To support the model, electrical and sound‐pressure level measurements in helium, argon, and air are presented.

ISSN:0001-4966    

DOI:10.1121/1.394762

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

The error in narrow‐band analytical or physical model predictions is estimated for the example of a harmonic force‐driven rectangular plate. It is shown that a 5% uncertainty in input parameters defining structural dimensions, material properties, and source location may account for errors in a predicted transfer function exceeding 10 dB over a reasonably broad bandwidth. It is also shown that this error increases 6 dB per doubling of the (percent) uncertainty. These results imply that in the absence of incoherent averaging, either temporal, spatial, or ensemble, expectations for favorable comparisons of structural acoustic predictions among models, or between model and prototype, may often be unrealistic.

ISSN:0001-4966    

DOI:10.1121/1.394763

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

An objective measure of the quality of speech communications channels was developed and described by Steeneken and Houtgast [J. Acoust. Soc. Am.67, 318–326 (1980)]. By calculating the speech transmission index (STI), this method provides an estimate of speech intelligibility for a variety of communication distortions, but the method has been validated only for the Dutch language. For this reason, questions arise about its applicability for use with English. Using the standard Harvard PB‐word test for speech intelligibility, it was shown that the STI method is a valid method for testing the speech transmission of communications channels intended for use with the English language. New STI curves were generated for both the English PB‐word test and the Modified Rhyme Test.

ISSN:0001-4966    

DOI:10.1121/1.394764

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

摘要:

Research in the use of physical measures to evaluate speech intelligibility is showing promising results, and a device for measuring the speech transmission index has been developed [Technical Notes and Research Briefs, J. Acoust. Soc. Am.71, 1612 (1982)]. For many important applications of voice testing, the state of the art has not yet reached a point where such a device can be substituted for standard intelligibility tests using listeners. The two major problems are: (1) The standard error of estimate is too large to make reliable comparisons in the range that would be of interest for selecting among competing methods; and (2) it is not clear that any but the simplest adjustments to voice systems that improve the STI also improve intelligibility, or that a change that improves intelligibility necessarily improves the STI.

ISSN:0001-4966    

DOI:10.1121/1.395129

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.395141

出版商:Acoustical Society of America    

年代:1987

数据来源: AIP