Volume 104, Issue 6, December 1998
- acoustical news—usa
- acoustical news—international
- book reviews
- reviews of acoustical patents
- selected research articles 
- general linear acoustics 
- aeroacoustics, atmospheric sound 
- underwater sound 
- ultrasonics, quantum acoustics, and physical effects of sound 
- transduction 
- structural acoustics and vibration 
- noise: its effects and control 
- acoustical measurements and instrumentation 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech perception 
- music and musical instruments 
- bioacoustics 
- letters to the editor
Index of content:
- BOOK REVIEWS
104(1998); http://dx.doi.org/10.1121/1.423953View Description Hide Description
- REVIEWS OF ACOUSTICAL PATENTS
104(1998); http://dx.doi.org/10.1121/1.423915View Description Hide Description
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 at http://www.uspto.gov.
- SELECTED RESEARCH ARTICLES 
Wave decomposition of the vibrations of a cylindrical shell with an automated scanning laser vibrometer104(1998); http://dx.doi.org/10.1121/1.423956View Description Hide Description
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 wavevector 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.
Sound absorption in concert halls by seats, occupied and unoccupied, and by the hall’s interior surfaces104(1998); http://dx.doi.org/10.1121/1.423957View Description Hide Description
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.
- GENERAL LINEAR ACOUSTICS 
104(1998); http://dx.doi.org/10.1121/1.423958View Description Hide Description
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 noisegenerated 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 noisegenerated 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.
The high-frequency asymptotic description of pulses radiated by a circular normal transducer into an elastic half-space104(1998); http://dx.doi.org/10.1121/1.423959View Description Hide Description
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.
A fast method for simulating the propagation of pulses radiated by a rectangular normal transducer into an elastic half-space104(1998); http://dx.doi.org/10.1121/1.423960View Description Hide Description
A new fast method for simulating the propagation of pulses radiated by a rectangular normal ultrasonic transducer which is directly coupled to an isotropic and homogeneous elastic half-space is proposed. First, the so-called two-tier approach introduced in Fradkin et al. [“The radiating near-field asymptotics of a time-harmonic circular normal ultrasonic transducer in an elastic half-space,” J. Acoust. Soc. Am. 104, 1178–1187 (1998)] and the uniform stationary phase method are used to obtain both nonuniform and uniform high-frequency asymptotics of the time-harmonic field. Then, the transient field is described by means of harmonic synthesis. The nonuniform asymptotics elucidate the physics and all the asymptotics give explicit dependence of the radiated waves on model parameters. The formulas are applicable in the radiating near field that is the near field with the evanescent wave zone excluded. The asymptotics involve in geometrical regions elementary and inside boundary layers, well-known special functions (Fresnel integral and generalized Fresnel integral). The code based on the uniform asymptotics has been tested in all regions against an exact numerical solution. It is at least times faster but in many realistic cases the accuracy does not suffer. The trains of pulses generated by rectangular and circular transducers are compared.
104(1998); http://dx.doi.org/10.1121/1.423961View Description Hide Description
The method of fundamental solutions (MFS) is applied to acoustic scattering and radiation for axisymmetric bodies and boundary conditions. The fundamental solution of the governing equation and its normal derivative, which are required in the formulation of the MFS, can be expressed in terms of complete elliptic integrals, which are evaluated using library software. The method is tested on several problems from the literature and the results compared with existing solutions. Numerical experiments demonstrate that the fictitious eigenfrequency problem which is encountered with the boundary element method is not present in the MFS.
104(1998); http://dx.doi.org/10.1121/1.423962View Description Hide Description
The finite-difference time-domain(FDTD) method provides a simple and accurate means of simulating a wide range of acoustic wave propagation problems. Unfortunately, the method has a voracious appetite for computational resources. For example, to accurately model scattering from a continuously varying pressure-release boundary, an FDTD grid is typically required that has a much finer discretization than is necessary to model propagation in a homogeneous space. Such a fine discretization can become prohibitive when considering large-scale problems. Two simple conformal techniques are presented for acoustic FDTD simulations of problems involving pressure-release boundaries. These techniques, which rely upon splitting velocity cells adjacent to the pressure-release boundary, significantly improve the accuracy of the results over those of the standard “staircase” representation of the boundary. These methods permit the use of a coarser FDTD grid than would otherwise be practical and yet add negligible computational cost. The improved accuracy of these split-cell techniques is shown for both a spherical scatterer and a spherical resonator.
104(1998); http://dx.doi.org/10.1121/1.423963View Description Hide Description
Wave propagation characteristics are studied of a fluid-filled, finite-length anisotropicviscoelastic pipe—a flexible hydraulic hose. An analytical model in transfer matrix form is developed for relating the pressure and flow ripples at hose upstream and downstream. The anisotropicviscoelasticity of the hose wall, the coupled vibration of the hose and the fluid, and the effect of possible longitudinal resonances of the finite-length hose are considered. The static mechanical properties and frequency-dependent mechanical properties of the hose wall are determined by means of specially designed static expansion method and optimal searching method separately. Experimental confirmation is made over a wide frequency range by using an experimental procedure for measuring the transfer matrix parameters. By comparing the predicted and measured results of the hoses with different lengths, it is shown that the model yields fairly good results in a frequency range of around 0–3 kHz and even may predict the influence of longitudinal resonances of the hose wall on the wave propagation of fluid in the hose. The effectiveness of the experimental methods and procedure proposed here are also verified.
104(1998); http://dx.doi.org/10.1121/1.423964View Description Hide Description
The transient diffraction of a plane step pressure pulse by a hard sphere is studied via the modal series solution in a neoclassical fashion. With the advent and availability of more powerful computers and increased sophistication of computational algorithms, it is now possible to (1) accurately compute the time histories of a sufficiently large number of terms of the modal series, and (2) use the Cesàro summation to completely eradicate the Gibbs’ phenomenon effects. This approach can be utilized to obtain the diffracted field in the entire space–time region. In particular, a complete treatment is developed for the diffracted field at the shadow boundary and in its neighborhood where heretofore no satisfactory analytical solution exists.
104(1998); http://dx.doi.org/10.1121/1.423916View Description Hide Description
The acoustic power emitted by a point monopole sound source in the vicinity of an elastically suspended, baffled, circular piston is investigated. The sound source is located on the axis of symmetry at distance d above the piston. A closed-form analytic expression is derived for the power flow emitted by the source in terms of the radiation impedance of a baffled piston. The dependency of the result on the various parameters of interest is investigated numerically, while simple, analytical approximations are given in a parameter region that defines the near field. These parameters include: ka, kd, and γ, where is the acoustic wave number, ω is the circular frequency of the source, a is the piston radius, is the natural frequency of the spring mounted piston, is the ratio of the volume densities of mass of the piston and the fluid, while h is the thickness of the piston disk and γ is the damping coefficient of the dashpot.