摘要:

Approximations for the frequency of the new resonance of a vapor bubble associated with evaporation and condensation are derived from the equations of ’’Vapor bubble dynamics’’ [R. D. Finch and E. A. Neppiras, J. Acoust. Soc. Am. 53, 1402–1410 (1973)]. Previous predictions of the new resonance frequency ω were obtained by numerically solving a secular equation. The purpose of the approximations is to elucidate the significant parameters; for example, the surface tension σ is predicted to greatly influence ω. When the liquid’s thermal conductivitykis sufficiently large, ω∝σ2/3 R−8/3, whereRis the equilibrium radius of the bubble; smallkgives ω∝σ2 R−4. The approximations are substantiated by comparisons with numerical results for water, nitrogen, and helium. Criteria for their use are presented. Effects of evaporation–condensation resonance on radiation pressure and extinction of sound are suggested.

ISSN:0001-4966    

DOI:10.1121/1.383507

出版商:Acoustical Society of America    

年代:1979

数据来源: AIP

摘要:

The method of straightforward expansion is applied to acoustic waves in a half‐space with sinusoidal boundary. It is found that the expansion is uniform. Propagating waves show their dependence on the undulations of the surface in a proportional manner to the order of the terms. Moreover, it is found that for certain values of wavenumbers the propagating waves have terms that are body waves.

ISSN:0001-4966    

DOI:10.1121/1.383508

出版商:Acoustical Society of America    

年代:1979

数据来源: AIP

摘要:

The extremals of the minimal layer thickness problem for reflectance modification, given monochromatic waves at normal incidence and real material parameters, are analyzed. The structures of sublayer sequences leading to minimal total layer thickness, when both the density and the dilatation modulus are allowed to vary independently are presented. It is found that there exist two different sublayer sequences. Both are periodic with unit cells of four layers. Minimal sequences for the corresponding one‐parameter problems are obtained as limiting cases.

ISSN:0001-4966    

DOI:10.1121/1.383509

出版商:Acoustical Society of America    

年代:1979

数据来源: AIP

摘要:

The simple source formulation is extended to the case of several smooth, rigid obstacles of arbitrary shape. Numerical calculations are presented for scattering by two circular cylinders and by two elliptical cylinders. Results are checked by use of both the reciprocity principle and the optical theorem and are found to be quite good in all cases.

ISSN:0001-4966    

DOI:10.1121/1.383510

出版商:Acoustical Society of America    

年代:1979

数据来源: AIP

摘要:

An analog circuit has been constructed to convert speech (vowels) to Lissajous‐type oscilloscope patterns in real time. The method is like that described by Boston [Brit. J. Audiol. 7, 95–101 (1973)], but includes circuit modifications to improve naturalness of lip outline and articulatory change. The speech signal receives preemphasis resembling ear canal resonance and is split into two channels. Two voltages, one proportional to 200–1000 Hz energy (F1) and the other proportional to 200–3000 Hz energy (F2 in front vowels,F1 in back vowels), are generated to control a multiplier and divider, respectively, which vary levels of sinusoidal signals to form the height and width of the lip outline. Resulting patterns resemble lip shapes of vowels in natural speech. Vowel‐confusion matrices obtained by lipreading the oscilloscope display (with speech input) are similar to those obtained by lipreading the talker’s face directly.

ISSN:0001-4966    

DOI:10.1121/1.383511

出版商:Acoustical Society of America    

年代:1979

数据来源: AIP

摘要:

Two versions of the ’’10 dB down–5 dB up’’ rule were computerized: (1) with a ’’lax’’ time‐window response validation in which a subject had to press and release a button within the window of 15–3750 ms after onset of a 1‐s tone in his earphone (this was designed to simulate the condition often found in manual audiometry) and (2) with a ’’strict’’ condition in which he had to respond within 60–795 ms after onset of the toneandrelease the button within 15–750 ms following the tone. A threshold‐seeking run was continued using 5‐dB steps until the threshold had been crossed six times. With 24 subjects it was found that 13 of 288 runs did not yield the ’’ASHA’’ criterion (three ascending series ending on the same hearing level (HL), out of any six or fewer consecutive series), but of these 13 runs all but one run did meet the ’’ANSI’’ criterion (two ascending series ending on the same HL, out of any three or fewer consecutive series). The ANSI Hearing Threshold Levels (HTL’s) were as reliable on test–retest as the ASHA and yielded essentially the same means. An ANSI HTL was established within four or fewer ascending series for 95% or more of the runs, while an average of five extra stimuli was needed to pursue the run until an ASHA HTL was achieved (a savings of nearly 5 min per person). It was recommended that the ANSI criterion for HTL be adopted for many audiometric situations, that a maximum of four ascending series be completed in any single threshold‐seeking run, and that rather strict time windows be set within which onset and offset responses may register.

ISSN:0001-4966    

DOI:10.1121/1.383512

出版商:Acoustical Society of America    

年代:1979

数据来源: AIP

摘要:

It is shown that the author’s work contains no known errors at this time and that there appears to be no discrepancy between his work and that of Hannan and Thomson (1973).

ISSN:0001-4966    

DOI:10.1121/1.383513

出版商:Acoustical Society of America    

年代:1979

数据来源: AIP

摘要:

Buckingham uses a simple unshaded vertical array in a waveguide. The simple unshaded vertical array is an inefficient receiver because it does not match the eigenfunctions of the waveguide. For his noise sources he uses free space functions instead of the eigenfunctions of the waveguide. This letter clarifies these aspects of his paper and gives a procedure for designing an optimum array processing system. The analysis shows that the main advantage of using a vertical array is to filter the different modes and when the mode spectrums of the signal transmission and noise are the same there may be little or no gain of the signal‐to‐noise power ratio. The procedure also gives upper and lower limits of the signal‐to‐noise ratio for vertical arrays in waveguide transmission.

ISSN:0001-4966    

DOI:10.1121/1.383514

出版商:Acoustical Society of America    

年代:1979

数据来源: AIP

摘要:

The author responds to Clay’s comments regarding the plane‐wave representation of the noise field and the choice of unshaded array.

ISSN:0001-4966    

DOI:10.1121/1.383515

出版商:Acoustical Society of America    

年代:1979

数据来源: AIP

摘要:

Calculation of the mutual impedance between two plane pistons in an infinite plane baffle involves a fourfold integration over the areas of the two pistons. In general, all of these integrations must be done numerically. However, for simple piston shapes, a change of variable can reduce two of the integrations to triviality leaving only two to be computed numerically. Results are presented for half‐wavelength‐diameter circular pistons and half‐wavelength‐dimension square pistons.

ISSN:0001-4966    

DOI:10.1121/1.383516

出版商:Acoustical Society of America    

年代:1979

数据来源: AIP