摘要:

Air bubbles on the surface of a sonar transducer cause disturbances in the calibration response. Several materials have been used at various facilities to cause the air bubbles to release more easily from the transducer surface. This report explains the mechanism of these surface active materials and compares them in terms of surface tension in solution, persistence on a rubber surface, and compatibility with other materials. Also reported are the results of field tests of each of the surface active materials on ten soiled transducers. The best materials proved to be Aerosol OT‐100R,a combination of OT‐100 and JoyR detergent, and JoyR detergent alone.

ISSN:0001-4966    

DOI:10.1121/1.392459

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

The exact frequency equation for the free vibrations of a pyroelectric (thermo‐piezoelectric) layer of (6 mm) class is obtained. The surfaces of the layer are kept traction free, completely coated with electrodes which are shorted and thermally insulated. The symmetric and the antisymmetric modes of vibration are discussed numerically. The dispersion curves have been presented graphically for a barium titanate (BaTiO3) layer.

ISSN:0001-4966    

DOI:10.1121/1.392460

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

This paper describes the optimal design of a foil electret earphone for use in telephony. The sensitivity (ratio of the sound pressure generated to the signal supplied) was maximized while meeting material, geometric, and performance constraints. First, a generalized reduced gradient optimization scheme based on the leading order approximations to the diaphragm motions was used. Second, the region of the approximate optimum was examined and an exhaustive search conducted for the optimal design based on exact numerical solution for the diaphragm motion. The results indicate that it is theoretically possible to design a foil electret earphone suitable for telephony which produces a sound pressure level of just over 90 dB in response to a 1‐V rms signal. The optimum earphone has a center circular portion surrounded by an annulus and uses thin, highly tensioned Mylar as a diaphragm. The electret material is mounted on the back electrode.

ISSN:0001-4966    

DOI:10.1121/1.392461

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

The effects of carbon black type and loading, and variation of base polymer, on a series of polychloroprene rubbers (neoprenes) have been investigated. Two common types of neoprenes, each with a lead oxide cure system, were used. The acoustic responses of these materials were characterized for extensional wave propagation in air by a resonance technique and longitudinal wave propagation in water through the use of a high‐frequency sing‐around device and an underwater acoustic impedance tube. The viscoelastic properties of neoprene elastomers were found to be strongly influenced by both the degree of loading and average particle size of the carbon black used. The results are discussed in terms of mechanisms of interaction between the carbon black filler and the gum phase of the elastomer.

ISSN:0001-4966    

DOI:10.1121/1.392462

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

The estimated sound intensity is compared to the exact intensity in order to study the precision of active sound intensity measurement, for the cases of a simple progressive field and any sort of nonprogressive fields. The progressive field is produced by an harmonic monopole, whereas the nonprogressive field is produced by two harmonic monopoles of variable strength ratio and geometric conditions. The analysis is performed in the time domain. In the progressive field case, a general formulation of the error is obtained which simplifies in limiting cases to forms already published in the literature. In the nonprogressive field case, emphasis is put on the formulation of the exact phase gradient and of the total pressure field resulting from the two sources. The formulation of the uncertainty points out considerable errors at low frequencies due to instrumental phase mismatch and at high frequencies due to finite approximation of amplitude and of the phase gradient. Finally, the ratio of the sound intensity to the pressure as an indicator of the accuracy of sound intensity measurement is discussed.

ISSN:0001-4966    

DOI:10.1121/1.392463

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

Computer‐steered microphone arrays provide an attractive sound‐transducing means for interactive communication by sizable groups of talkers. But the spatial acuity of arrays typically varies with frequency, exhibiting diminishing beamwidth as frequency increases. Frequency‐weighting the receiving elements is one means to mitigate the variation and to achieve more uniform beamwidth over the useful frequency range. Acoustic low‐pass filtering, accomplished in the physical housing of the receivers, provides effective and economical modification of beamwidth.

ISSN:0001-4966    

DOI:10.1121/1.392464

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

The amount of cavitational activity occurring within an aqueous sample exposedinvitroto therapeutic intensities of MHz ultrasound is increased if the sample chamber is rotated or its contents are stirred or injected under pressure. This enhancement of cavitation apparently results either from the generation of new nuclei because of contact of the magnetic bar with the microscopically uneven surface of the sample holder or from relocation of existing nuclei so as to make them more active within the same acoustic field. Further, this enhancement of cavitational activity was affected by the applied acoustic pressure, the rate of agitation, the volume of the sonication chamber,the position of the stirrer within the beam, and the type of surface upon which stirring was performed.

ISSN:0001-4966    

DOI:10.1121/1.392465

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

In three related experiments, listeners judged the affect conveyed by short recorded utterances in which the voice quality, intonation contour type, and fundamental frequency range had been systematically and independently manipulated. (Contour and range were manipulated using digital resynthesis of naturally spoken utterances.) Analyses of variance of the results showed that range and contour, and less clearly range and voice quality, had independent effects on the way the utterances were judged. The results also strongly suggest that these differences are independent of effects due to interspeaker differences and to differences of verbal content. Finally, analysis of the results suggests that differences ofF0 range, as is commonly assumed, have continuous rather than categorical effects on affective judgments.

ISSN:0001-4966    

DOI:10.1121/1.392466

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

This paper reports acoustic measurements and results from a series of perceptual experiments on the voiced–voiceless distinction for syllable‐final stop consonants in absolute final position and in the context of a following syllable beginning with a different stop consonant. The focus is on temporal cues to the distinction, with vowel duration and silent closure duration as the primary and secondary dimensions, respectively. The main results are that adding a second syllable to a monosyllable increases the number of voiced stop consonant responses, as does shortening of the closure duration in disyllables. Both of these effects are consistent with temporal regularities in speech production: Vowel durations are shorter in the first syllable of disyllables than in monosyllables, and closure durations are shorter for voiced than for voiceless stops in disyllabic utterances of this type. While the perceptual effects thus may derive from two separate sources of tacit phonetic knowledge available to listeners, the data are also consistent with an interpretation in terms of a single effect; one of temporal proximity of following context.

ISSN:0001-4966    

DOI:10.1121/1.392467

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP

摘要:

This study investigates perceptual differences between natural and synthesized speech as measured by the effects of stimulus repetition on test item identification accuracy. The results show that identification accuracy is enhanced by repetition for natural speech but not for synthesis, suggesting that there are appreciable differences in their perceptual properties, at least inder the conditions of this experiment.

ISSN:0001-4966    

DOI:10.1121/1.392468

出版商:Acoustical Society of America    

年代:1985

数据来源: AIP