ISSN:0001-4966    

DOI:10.1121/1.421047

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Abstract not available.

ISSN:0001-4966    

DOI:10.1121/1.419967

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.419978

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.419969

出版商:Acoustical Society of America    

年代:1997

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:10.1121/1.419980

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

In this paper, a theoretical formulation is proposed to describe a time-reversal process in a solid medium with two propagation modes, longitudinal and transverse waves. A plane time-reversal mirror (TRM) is used, installed in a fluid which is in contact with the solid through a plane interface parallel to the TRM. The basic approach is similar to the case of a plane fluid–fluid interface [D. Cassereau and M. Fink, J. Acoust. Soc. Am.96, 3145–3154 (1994)]; it is extended to take into account the different wave types. It is shown that the TRM is able to recreate properly in time and space the reversed fields of the longitudinal wave and the vertical polarizationSVof the transverse waves, but not the horizontal polarizationSH.The focusing quality of the backpropagating waves is limited by their respective wavelengths, so the slowerSVwave can be better focused. Additional, unwanted wavefronts are created in the solid, too, but they are of weak amplitude and they are not focused. Numerical simulations illustrate the dependence of the focal pattern on parameters like distance–source interface, size, and eccentricity of the mirror.

ISSN:0001-4966    

DOI:10.1121/1.420094

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

A noncontact acoustical system has been developed which measures Young’s modulus of solid materials at high temperature with⩽0.05%accuracy. The system employs capacitive (or electrostatic) transducers to excite and detect vibrations of millimeter-sized resonant tuning forks, whose resonance frequencies alter with changing temperature and material properties. The use of tuning forks in their fundamental symmetric modes of vibration provide resonances of highQ’s and eliminate irreversible frequency and drift effects that occur with other forms of resonator. The use of noncontact capacitive transducers reduces the damping and stresses that otherwise occur with contacting transducers, and allows the system to be simply and accurately modeled. Both single crystal silicon tuning forks, and those manufactured from hydrided and unhydrided Zr–2.5%Nb, were investigated at temperatures up to 700 °C. The measured responses of silicon forks confirmed the system accuracy, and suggested that single-crystal silicon be standardized as a calibration material for acoustical measurement systems. Results obtained with Zr–2.5%Nb tuning forks allowed an accurate quantitative analysis of the effects of hydride dissolution and precipitation on Young’s modulus, and confirmed that Young’s modulus of hydrided Zr–2.5%Nb decreases in proportion to free hydrogen concentration. This experimental system should prove valuable for accurate modeling of high-temperature material transformations in solids.

ISSN:0001-4966    

DOI:10.1121/1.420095

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

A new variational formulation using integral equations for the resolution of a propagation problem in a viscous and thermally conducting fluid is investigated. Numerical techniques are applied to a geometry of revolution. Results are compared to an analytic solution for a cylindrical cavity filled with air. These results illustrate the effects of viscosity and thermal conductivity of air in the case of micro cavities.

ISSN:0001-4966    

DOI:10.1121/1.420050

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

A novel approach to reducing the matrix size associated with the boundary element/moment method solution of the problem of acoustic scattering from arbitrarily shaped closed bodies is presented in this paper. The key step in this approach is to represent the scattered field in terms of a series of beams produced by multipole sources located in acomplexspace. On the scatterer boundary, the fields generated by these multipole sources resemble the Gabor basis functions. By utilizing the properties of the Gabor series, guidelines for selecting the orders as well as locations of the multipole sources are developed. The present approach not only reduces the number of unknowns, but also generates a generalized impedance matrix with a banded structure. The accuracy of the proposed method is verified by using internal accuracy checks and by comparing the numerical results with the analytic solutions for spherical scatterers.

ISSN:0001-4966    

DOI:10.1121/1.420051

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

The phenomenon of excess attenuation due to audience seating, which is called “seat dip effect (SDE),” have been discussed in the case of a rather short-time interval including a direct sound and early arriving sound. However, it may be expected that the effect is diminished as the time interval increases, owing to the supplement of other arriving sounds. The first aim of this investigation is to clarify the effect of time interval on the SDE as well as the effect of other arriving sounds, by means of110-scale model experiments. For the mechanism of the phenomenon, a clear explanation has not yet been given. The second aim is to clarify the fundamental mechanism of the SDE. For this aim, a wave-scattering theory for a periodic surface and a simple wave reflection theory for a layered boundary surface are applied, and discussed in comparison with the experimental results. From this investigation, it became clear that the mechanism of the SDE can be easily explained by using these simple analytical models.

ISSN:0001-4966    

DOI:10.1121/1.420052

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP