摘要:

Abstract not available.

ISSN:0001-4966    

DOI:10.1121/1.4734350

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Abstract not available.

ISSN:0001-4966    

DOI:10.1121/1.423914

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.424219

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.424230

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.423953

出版商:Acoustical Society of America    

年代:1998

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:10.1121/1.423915

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Elastic waves propagating in a cylindrical shell have been detected by an automated scanning laser vibrometer designed to record both in-plane and out-of-plane surface motion over the surface of the shell (32 points axially and 32 points circumferentially). The structure was freely suspended in air and excited radially by a shaker at a single frequency, either below or above the ring frequency of the shell. A wave vector analysis of the data was performed with a fast Fourier transform and an overdetermined modified extended Prony method. The results clearly show the presence of longitudinal, shear, and flexural waves above the ring frequency. In addition, the Prony method reveals the presence of evanescent waves due to mode conversion of the propagating waves near the ends of the shell. Below the ring frequency, two types of in-plane waves and flexural waves were identified. The results are in excellent agreement with predictions from the dispersion curves for thin shells.

ISSN:0001-4966    

DOI:10.1121/1.423956

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

From experimental data in concert and opera halls, absorption coefficients were determined for audience seating, unoccupied and occupied, of different constructions, and for gypsum, wood, plaster, and concrete interior surfaces of various thicknesses and densities. A total of ten halls were involved in the bare hall (before seats were installed) analysis, yielding “residual” absorption coefficients, i.e., coefficients for those areas not including the areas to be covered by the seating. In ten halls reverberation times were measured after installation of the seats (unoccupied) and in seven of these halls at concerts with seats fully occupied. The seating absorption coefficients are presented for “acoustical” audience areas, i.e., with a 0.5-m-wide edge around each seating block. The results are compared with the data of Appendix 5 in Beranek [Concert and Opera Halls: How They Sound(Acoustical Society of America, Woodbury, NY, 1996)]. The sound absorption data presented for interior surfaces and audience areas should permit more accurate estimation of reverberation times as a function of frequency for large halls during the planning stage.

ISSN:0001-4966    

DOI:10.1121/1.423957

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

The moving frame acoustic holography method, which can increase the aperture size and spatial resolution of a hologram was recently proposed [H.-S. Kwon and Y.-H. Kim, J. Acoust. Soc. Am.103, 1734–1742 (1998)]. This method continuously sweeps a stationary sound field by using a line array of microphones so that the hologram of a scanned plane can be obtained. This method enables us to visualize the noise generated by moving noise sources based on near-field acoustic holography. However, a drawback is that it can be applied only to sinusoidal components. This limits its practical application. In practice, bandlimited and transient noise, as well as a sinusoidal component, must be dealt with in order to effectively control the noise generated by the moving noise sources. This paper addresses a way to improve the moving frame acoustic holography method so that it can be applied not only to sinusoidal components, but also to a coherent bandlimited noise. The practical applicability of the improved method is also verified by experiments.

ISSN:0001-4966    

DOI:10.1121/1.423958

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

A new method for simulating the propagation of pulses radiated by a circular normal ultrasonic transducer which is directly coupled to a homogeneous and isotropic elastic half-space is proposed. Both nonuniform and uniform high-frequency asymptotics inside geometrical regions as well as boundary layers (penumbra, an axial region, and a vicinity of the critical rays) have been used to describe the transient field by means of harmonic synthesis. The nonuniform asymptotic formulas involving elementary or well-known special functions elucidate the physics of the problem and give explicit dependence of the radiated waves upon the model parameters. The formulas are applicable in the radiating near field which is the near-field with the evanescent wave zone excluded. The code based on the uniform asymptotics has been tested in all regions against an exact numerical solution. It is orders of magnitude faster, but in many realistic cases the accuracy does not suffer. The limits of applicability of the model have been established.

ISSN:0001-4966    

DOI:10.1121/1.423959

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP