摘要:

Recent results showing the equivalence of mode attenuation per cycle and reflection loss of the equivalent ray did not hold in shallow water with a small number of modes. The failure is demonstrated to be linked to the concept and definition of a mode cycle distance for low mode density. Attenuation rates of modes and average attenuation rates of rays are now shown to be equal for all mode densities, provided the attenuation is not too large and the ray cycle distance is taken as the sum of the geometrically traced ray distance and the boundary beam displacement.

ISSN:0001-4966    

DOI:10.1121/1.385073

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

An exact solution for the field due to a point source above a homogeneous and isotropic porous ground has been derived in terms of a single branch line integral and a pole residue. The expected properties of the porous ground lead to a less complex solution than that usual to geophysics or underwater acoustics. The method of steepest descents modified by subtraction of the pole enables the derivation of an approximate solution for an externally reacting boundary. The precise nature of the further approximations that follow the assumption of a locally reacting (or impedance) boundary is made explicit and the role of the surface wave pole is clarified. Finally, the existing solutions for a locally reacting boundary are compared, and with one exception they are shown to be identical.

ISSN:0001-4966    

DOI:10.1121/1.385074

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

The nonlinear oscillation of a bubble in compressible hydraulic oils subject to periodic pulsating pressure was theoretically analyzed. According to the numerical calculations, the effect of compressibility of liquid on the oscillation of a bubble were clarified. That is, (1) the effect of compressibility is appreciable where the amplitude is large; (2) when compressibility is considered, the pressure threshold increases; (3) in the subharmonic of order 1/2, the effect of compressibility on the pressure threshold is almost constant over a wide range of initial bubble radiusR0; (4) the effect of compressibility on the relation between ω/ω0(a ratio of the circular frequencies of pulsating pressure and a bubble) and pressure threshold of the subharmonics 1/2 and 1/3 is almost constant covering the wide range of ω/ω0.

ISSN:0001-4966    

DOI:10.1121/1.385075

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

In the present paper, an equation of the state of compressible hydraulic oils was derived by using the relation between pressure and bulk modulus obtained by Klaus–O’brien. As a result, it was shown that in the case where the bulk modulus was shown by a linear function of pressure, Tait’s equation as an empirical formula was obtained and the constants in the equation were derived theoretically. Further, using the derived equation, the equation of bubble motion was derived by means of an approximate solution using the Poincaré–Lighthill–Kuo coordinate perturbation method. The effects of liquid compressibility on the bubble behavior and impulse pressure were numerically clarified.

ISSN:0001-4966    

DOI:10.1121/1.385076

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

A model for an imperfectly bonded interface between two elastic media is proposed. Displacement across this surface is not required to be continuous. The displacement discontinuity, or slip, is taken to be linearly related to the stress traction which is continuous across the interface. For isotropic interface behavior, there are two complex frequency dependent interface compliances, ηNand ηT, where the component of the slip normal to the interface is given by ηNtimes the normal stress and the component tangential to the interface is given by ηTtimes the shear stress and is in the same direction. Reflection and transmission coefficients for harmonic plane waves incident at arbitrary angles upon a plane linear slip interface are computed in terms of the interface compliances. These coefficients are frequency dependent even when the compliances are real and frequency independent. Examples of the effects of buried slip interfaces on reflection coefficient spectra and on Love‐wave dispersion relations are presented.

ISSN:0001-4966    

DOI:10.1121/1.385077

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

The current International Standard (ISO 2631, 1978) on whole‐body vibration defines a complex relation between discomfort and duration of vibration exposure. There are doubts concerning the accuracy of this relation and there are difficulties and dangers in its application to some non‐steady‐state conditions. This paper compares the ISO time‐dependency with those based on root mean square (rms) and root mean quad (rmq) averaging of levels over time. [The rmq averaging procedure is based on experimental studies reported by Griffin and Whitham (1980) J. Acoust. Soc. Am. 68, 1277–1284.] It is shown that although the rmq procedure was developed from studies involving only short duration vibration, it defines a time dependency which may be acceptable for much longer periods.

ISSN:0001-4966    

DOI:10.1121/1.385078

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

The critical‐band rate as well as the critical bandwidth are functions of frequency. These dependencies have been given in table form. For effective use of these values in computers, relatively simple equations are given to express the dependence of critical‐band rate on frequency with an accuracy better than 0.2 Bark and that of critical bandwidth on frequency with an accuracy better than 10% over the whole auditory range.

ISSN:0001-4966    

DOI:10.1121/1.385079

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

The model of atmospheric air given in ANSI S1.26–1978 (’’Method for the Calculation of the Absorption of Sound by the Atmosphere’’) has been used to predict the frequency and humidity dependence of the sound speed in air. Good agreement with existing measurements is demonstrated, apart from an unexplained discrepancy at low relative humidity.

ISSN:0001-4966    

DOI:10.1121/1.385080

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Experimental measurements of acoustic pressure fields near the focal points of ultrasonic transducer‐lens systems are compared to calculations of a recently developed analytic technique. This method incorporates the Fresnel approximation to expand the field in terms of Gaussian–Laguerre functions to calculate the acoustic field for arbitrary placement of a lens in the nearfield of a circular transducer. The predicted field pattern symmetries near the focal region with a lens located either at one focal distance or at the transducer face are confirmed by experimental measurements made with a microsphere probe.

ISSN:0001-4966    

DOI:10.1121/1.385081

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.385228

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP