ISSN:0001-4966    

DOI:10.1121/1.414898

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.414899

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.414903

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:10.1121/1.414904

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

Relations between the design of a piano and the quality of its tone are reviewed and discussed from the point of view of an instrument designer. Topics include the effects on tone by the hammers, the voicing, the soundboard, the case, the string plate, and the design of the scale and strings, including longitudinal string modes, wrapped strings, and inharmonicity. Design limitations relating to materials, performance, or tone quality are noted. The effect of varying a parameter is described or illustrated graphically when feasible. Data comparing pianos of various size and design are shown. Examples are shown of the use of mobility measurements in assessing soundboard and string plate performance. The potential value of modal and finite element analysis in design work is noted. Although the piano is regarded by many people as fully developed, the author believes that there has never been a better time for improvement. Some directions for future work are indicated.

ISSN:0001-4966    

DOI:10.1121/1.414947

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

In this paper, the development of a space‐time finite element method for the solution of the transient acoustics problem in exterior domains is discussed. The space‐time formulation for the exterior acoustics problem is obtained from a time‐discontinuous Galerkin variational equation for coupled structural acoustics, specialized to the case of zero normal velocities on the wet surface, i.e., a rigid scatterer. The formulation employs a finite computational acoustic domain surrounding the scatterer and incorporates high‐order time‐dependent nonreflecting (radiation) boundary conditions on the fluid truncation boundary as ‘‘natural’’ boundary conditions in the space‐time variational equation, i.e., they are enforced weakly in both space and time. The result is an algorithm for direct transient analysis of acoustic radiation and scattering with the desired combination of good stability and high accuracy. The method is especially useful for the application of adaptive solution strategies for transient acoustics in which unstructured space‐time meshes are used to track wavefronts propagating along space‐time characteristics. Optimal stability estimates and convergence rates are reported together with two representative numerical examples involving transient radiation and scattering which illustrate the high‐order accuracy achieved by the method for the exterior acoustics problem.

ISSN:0001-4966    

DOI:10.1121/1.414887

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

A time‐domain computer algorithm that solves an augmented Burgers equation is described. The algorithm is a modification of the time‐domain code developed by Lee and Hamilton [J. Acoust. Soc. Am.97, 906–917 (1995)] for pulsed finite‐amplitude sound beams in homogeneous, thermoviscous fluids. In the present paper, effects of nonlinearity, absorption and dispersion (both thermoviscous and relaxational), geometrical spreading, and inhomogeneity of the medium are taken into account. The novel feature of the code is that effects of absorption and dispersion due to multiple relaxation phenomena are included with calculations performed exclusively in the time domain. Numerical results are compared with an analytic solution for a plane step shock in a monorelaxing fluid, and with frequency‐domain calculations for a plane harmonic wave in a thermoviscous, monorelaxing fluid. The algorithm is also used to solve an augmented KZK equation that accounts for nonlinearity, thermoviscous absorption, relaxation, and diffraction in directive sound beams. Calculations are presented which demonstrate the effect of relaxation on the propagation of a pulsed, diffracting, finite‐amplitude sound beam.

ISSN:0001-4966    

DOI:10.1121/1.414983

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

An analytical, approximate solution of the inviscid KZK equation, for a finite amplitude pulsed sound beam radiated by a Gaussian source, is obtained by means of the renormalization method. The method involves two main steps. First, the transient quasilinear field is obtained under an integral form. However, this weakly nonlinear approximation breaks down with increasing nonlinear effects. Its validity is then extended by inserting into it a nonlinear coordinate transform, so as to counterbalance nonuniform terms. The choice of the renormalization is made so as to handle, as best as possible, the formation of shock waves. Comparisons with the results of a finite‐differences scheme (‘‘Bergen code’’) show that, both on and off axis, for short and long pulses, the method is able to describe accurately the nonlinear distortion of the wave profile, the formation of shock waves, and their early evolution.

ISSN:0001-4966    

DOI:10.1121/1.414888

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

It is assumed that the solution to a problem is given in the form of a complex multiple Fourier series infinite in each of the original frequencies. In this paper a simple theorem shows that the absolute values of the individual frequency coefficients in the series are independent of the phase relation between the original frequencies. But the coefficient’s division into real and imaginary parts is phase dependent. When the ratios between the frequencies are not irrational numbers there exist in the sum several coefficients giving the same frequency, and hence, the total amplitude for a specific frequency depends on the phase. An example of application shows results from nonlinear acoustics where, e.g., the importance of original phase for parametric arrays can be estimated.

ISSN:0001-4966    

DOI:10.1121/1.414889

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

A theoretical model is presented that describes the interaction of frequency components in arbitrary pulsed elastic waves during one‐dimensional propagation in an infinite medium with extreme nonlinear response. The model is based on one‐dimensional Green’s function theory in combination with a perturbation method, as has been developed for a general source function by McCall [J. Geophys. Res.99(B2), 2591–2600 (Feb. 1994)]. A polynomial expansion of the equation of state is used in which four orders of nonlinearity in the moduli are accounted for. The nonlinear wave equation is solved for the displacement field at distancexfrom a symmetric ‘‘breathing’’ source with arbitrary Fourier spectrum imbedded in an infinite medium. The perturbation expression corresponds to a higher‐order equivalent of the Burgers’ equation solution for velocity fields in solids. The solution is implemented numerically in an iterative procedure which allows one to include an arbitrary attenuation function. Energy conservation is investigated in the absence of (linear) attenuation, and the notion of a hybrid (linear and nonlinear) dissipation is illustrated. Examples are provided showing the effect of each term in the perturbation solution on the spectral content of the waveform. Finally, the possibility of creating a parametric array for seismic exploration is briefly considered from a theoretical point of view.

ISSN:0001-4966    

DOI:10.1121/1.414890

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP