ISSN:0001-4966    

DOI:10.1121/1.414470

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.414472

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

The purpose of these acoustical patent reviews is to provide enough information for a Journal reader to decide whether to seek more information from the patent itself. Any opinions expressed here are those of the reviewers as individuals and are not legal opinions. Printed copies of United States Patents may be ordered at $3.00 each from the Commissioner of Patents and Trademarks, Washington, DC 20231. Patents are available via the Internet athttp://www.uspto.gov.

ISSN:0001-4966    

DOI:10.1121/1.414473

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.414533

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.414534

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

The reciprocal theorem of mathematical physics was not originated by Rayleigh. However, the theorem is presented, in several forms, with elegant clarity in hisTheoryofSound. Since its publication his book has influenced generations of physicists, particularly those working in acoustics. When combined with the parallel reciprocal theorem of electric‐circuit theory, it has proved to be invaluable to the subject of electroacoustics, on which is based the modern technology of acoustical measurements. In the ensuing 100 years since publication of his book, physicists have found the reciprocity principle to be valid in many areas of physics. However, the principle is not universally valid; we describe physical systems to which an antireciprocal theorem applies. Kelvin–Tait had, in effect, developed an antireciprocal theorem (for gyroscopic forces proportional to velocities) in a nonconservative mechanical system. The results in their 1879 book were introduced by Rayleigh in his second edition (1894), but without identification of an antireciprocal theorem. Particularly in the electroacoustics of transducers—microphones and loudspeakers—application of the reciprocal and antireciprocal theorems are of comparable usefulness. The latter theorem may be said to date from Faraday’s discovery of electromagnetic induction in 1831; the electrocmechanical action of an electromagnetic motor–generator satisfies an antireciprocal theorem.

ISSN:0001-4966    

DOI:10.1121/1.415227

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

In this paper it is shown how one can obtain the diameter and depth of a solid spherical inclusion in a solid half‐space directly from the location of the peaks of itsV(z) curve. Simplified expressions ofV(z) curves presented in this paper have been experimentally verified by generatingV(z) curves of a spherical inclusion in pure epoxy. The inclusion diameter and depth are predicted from the experimentally generatedV(z) curves. Experimental predictions are found to be very close to the true values; errors associated with all predictions are less than a few percent.

ISSN:0001-4966    

DOI:10.1121/1.414535

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

The problem of linear propagation of a time‐harmonic acoustic field in an infinite statistically homogeneous fluid is considered. The aim of this investigation is to calculate the effective constitutive parameters which determine the properties of a random fluid with respect to the mean field for the case of strong fluctuations of density and compressibility. This is achieved by using a bilocal approximation and a renormalization method. Special emphasis of the present paper is devoted to statistically anisotropic perturbations. It is shown, through analytic examples, that the statistical anisotropy of strong density fluctuations essentially modifies the random medium effective properties compared to the case of statistically isotropic perturbations, and has a significant effect on propagation characteristics of the mean acoustic field.

ISSN:0001-4966    

DOI:10.1121/1.415221

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

An efficient numerical scheme based on ray theory is developed for the analysis of elastic waves traveling over a fluid‐loaded smooth elastic shell of arbitrary shape. The shell’s surface is first discretized into a number of small patches. The local geometry of each patch is then approximated in a parametric form using bi‐cubic spline functions. A local curvilinear coordinate frame is defined on each patch. The ray trajectories and ray‐tube areas are obtained by solving a set of ordinary differential equations, the ray and transport equations, within each patch. Several numerical tests of the accuracy and efficiency of the scheme were carried out on spherical and ellipsoidal elastic shells. The numerical results for the spherical shell agree well with analytical solutions. The ray trajectories and the ray‐tube areas over an ellipsoidal shell with three distinct semiaxes clearly illustrate the inhomogeneous and anisotropic effects due to the variable curvature on the shell’s surface. It is also observed numerically that the magnitude of the ray‐tube area along a ray is directly correlated with the stability of its trajectory.

ISSN:0001-4966    

DOI:10.1121/1.414489

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

Wave statistical theory of the thermal acoustic radiation in a medium is presented on the basis of a model of hydrodynamic fluctuations. The wave stochastic equation is derived for the pressure fluctuations with given random mechanical forces. This theory is applied to the problems of the thermal fluctuations of the pressure in (1) an unbounded medium and (2) an acoustic resonator while taking into account the directivity diagram of a transducer. In the case of a resonator, the conditions for measuring of separate resonance peaks are estimated depending on the ratio of the transducer and the resonator dimensions and values of absorption of a medium.

ISSN:0001-4966    

DOI:10.1121/1.414490

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP