摘要:

Abstract not available.

ISSN:0001-4966    

DOI:10.1121/1.418083

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:10.1121/1.418090

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

This article on acoustic cavitation is a revision of a tutorial lecture presented at the Acoustical Society of America meeting in Austin, Texas, on 28 November 1994. The general approach adopted here differs from a review article in stressing the overarching themes that come under the category of acoustic cavitation, rather than being an encyclopedic reference on the topic. When possible, specific order-of-magnitude estimates have been given so that the reader can better understand the particular phenomena being described. The basic physics is discussed, and applications are reviewed with the goal of putting them in a useful context.

ISSN:0001-4966    

DOI:10.1121/1.418130

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

A novel method is presented to calculate the reflection coefficient of sound from a semi-infinite periodic system of elastic layers. Each layer may consist of sublayers, and may be either isotropic, or transversely anisotropic. The reflection coefficient is given in an explicit form for alternating solid and liquid layers at an oblique incidence of a sound wave as well as for all solid layers at normal incidence. For all solid layers at oblique incidence a quadratic matrix equation with respect to the input impedance matrix is obtained. The method of solving this equation and the coefficients of a transfer matrix for transversely isotropic layers are presented in the Appendices. Resonance properties of the system of layers follow from the results of computations of the frequency and angular dependencies.

ISSN:0001-4966    

DOI:10.1121/1.418155

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

A method is presented for the numerical calculation of a scalar wave propagating along a two-dimensional rough-sided or irregular waveguide. In this situation the wave becomes multiply scattered, with simultaneous interaction at the two boundaries. The field can be expressed in terms of a pair of coupled integral equations; these are derived and solved in an approach based on the parabolic integral equation method, which assumes that all energy is carried in a forward direction. An extended formulation encompassing backscatter is also derived, and a method given for its treatment. This paper serves in part to explain the computational results presented in B. J. Uscinski, “High-frequency propagation in shallow water,” J. Acoust. Soc. Am.98, 2702–2707 (1995).

ISSN:0001-4966    

DOI:10.1121/1.418099

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

Using the plane-wave expansion method, we study the propagation of elastic waves through two-dimensional (2-D) periodic composites which exhibit full band gaps for all the polarizations and directions of the displacements. Defect states created inside those band gaps are also studied by disturbing the periodicity of the lattice. Systems exhibiting such kinds of states can be used as acoustical filters.

ISSN:0001-4966    

DOI:10.1121/1.418156

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

A simple inverse acoustic algorithm using the Levenberg–Marquardt method is developed to estimate the sound velocity field as a function of depth from the transient measurements of the wave displacement at some suitable locations. The inverse calculations are performed based on the simulated exact and inexact measurement data to show the validity of the present study. Moreover, statistical analysis will also be considered here to determine both the best measurement position and the 99% confidence bounds. Results show that the accuracy of the estimated sound velocity and its sensitivity to the measurement errors depend on the number of measurement data, as well as the measured positions. The reliable inverse solutions can be obtained only when these two factors are chosen properly.

ISSN:0001-4966    

DOI:10.1121/1.418157

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

A model of a spherically focused piston transducer is developed in terms of boundary diffraction waves. The model represents the radiated pressure in terms of a direct wave and a one-dimensional edge wave integral. This decomposition allows the efficient calculation of the transducer beam in a form previously available only for a planar transducer. Numerical results for the simulation of the entire wave field of a transducer are given to illustrate the effectiveness of the formulation.

ISSN:0001-4966    

DOI:10.1121/1.418100

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

A time-domain numerical model for studying the influence of close barriers on sound levels at a large distance from a source is proposed. It is a combination of a near-field simulation with a near-field to far-field transform based on the Helmholtz–Kirchhoff integral. The near-field simulation is based on a finite-difference time-domain type discretization of a well chosen volume around sources and near objects. The numerical accuracy of the model is studied theoretically and experimentally for a particular sound field. The simulation example is a large power station transformer surrounded by barriers. The evaluation of sound levels in the highly multimodal environment is not trivial. It is performed in small frequency bands around the frequency of the typical pure tones emitted by the source.

ISSN:0001-4966    

DOI:10.1121/1.418101

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP

摘要:

One of the well-known methods of ultrasound focusing is the use of a transducer having the form of a concave spherical cap. In the theoretical analysis, O’Neil’s formula is widely used, which describes acoustic pressure on the axis of the transducer under the assumption that normal velocity of its surface is uniform. Usually, it is believed that modern piezoelectric focused sources are very close to this theoretical model. The paper presented describes results of experimental investigation which showed that there exists a significant disagreement between the observed acoustic field and that predicted by the theory of O’Neil. Two types of measurements have been made to clarify this problem. The acoustic pressure field of a focused piezoceramic transducer (with aperture diameter of 100 mm, radius of curvature of 100 mm, resonance frequency of 1 MHz) has been measured in a water tank using a miniature hydrophone. In addition, the radiator surface vibration has been studied in air using an optical interferometric technique. Theoretical analysis and the measurements show that the disagreement between the theory and the experiment is due to Lamb waves, which originate at the radiator edge, propagate along the piezoceramic plate without significant attenuation, and thus radiate additional acoustic perturbations.

ISSN:0001-4966    

DOI:10.1121/1.418102

出版商:Acoustical Society of America    

年代:1997

数据来源: AIP