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Dec 2003

Volume 114, Issue 6, pp. 2973-3424

References to Contemporary Papers on Acoustics
(published as Part 2 of this issue)

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Sound focusing in rooms. II. The spatio-temporal inverse filter

Sylvain Yon, Mickaël Tanter, and Mathias Fink

J. Acoust. Soc. Am. Volume 114, Issue 6, pp. 3044-3052 (2003); (9 pages) | Cited 5 times

Online Publication Date: 02 Dec 2003

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The potential of time reversal processing for room acoustics has been extensively investigated in the companion of this paper [J. Acoust. Soc. Am. 113(3), 1533–1543 (2003)]. In particular, a simple implementation of a loudspeaker time reversal antenna able to take advantage of the multiple reflections in reverberating rooms demonstrates its potential for audible range acoustics while improving focusing both in space and time. However, loss of information (e.g., sound absorption in walls or nonequalized bandwidths of the loudspeakers) during a time reversal experiment degrades the quality of time reversal focusing. In this paper, a more sophisticated technique called spatio-temporal inverse filtering is investigated that achieves time and space deconvolution of the propagation operator between the loudspeakers antenna and a set of microphones embedded inside the insonified volume. Theoretical and experimental comparisons between time reversal and inverse filter focusing are presented. Finally, advantages and limitations of both focusing approaches are highlighted. © 2003 Acoustical Society of America.
Show PACS
43.20.El Reflection, refraction, diffraction of acoustic waves
43.60.Gk Space-time signal processing, other than matched field processing
43.38.Hz Transducer arrays, acoustic interaction effects in arrays

Transient fluid–structure interaction of elongated bodies by finite-element method using elliptical and spheroidal absorbing boundaries

S. K. Bhattacharyya and R. Premkumar

J. Acoust. Soc. Am. Volume 114, Issue 6, pp. 3053-3064 (2003); (12 pages)

Online Publication Date: 02 Dec 2003

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In a domain method of solution of exterior scalar wave equation, the radiation condition needs to be imposed on a truncation boundary of the modeling domain. The Bayliss, Gunzberger, and Turkel (BGT) boundary dampers, which require a circular cylindrical and spherical truncation boundaries in two-(2D) and three-(3D)-dimensional problems, respectively, have been particularly successful in the analysis of scattering and radiation problems. However, for an elongated body, elliptical (2D) or spheroidal (3D) truncation boundaries have potential to reduce the size of modeling domain and hence computational effort. For harmonic problems, such extensions of the first- and second-order BGT dampers are available in the literature. In this paper, BGT dampers in both elliptical and spheroidal coordinate systems have been developed for transient problems involving acoustic radiation as well as fluid–structure interaction and implemented in the context of finite-element method based upon unsymmetric pressure-displacement formulation. Applications to elongated radiators and shells are reported using several numerical examples with excellent comparisons. It is demonstrated that significant computational economy can be achieved for elongated bodies with the use of these dampers. © 2003 Acoustical Society of America.
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43.20.Px Transient radiation and scattering
43.20.Tb Interaction of vibrating structures with surrounding medium
43.40.Yq Instrumentation and techniques for tests and measurement relating to shock and vibration, including vibration pickups, indicators, and generators, mechanical impedance

Acoustic field of a wedge-shaped section of a spherical cap transducer

Jeffrey A. Ketterling

J. Acoust. Soc. Am. Volume 114, Issue 6, pp. 3065-3075 (2003); (11 pages)

Online Publication Date: 02 Dec 2003

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The acoustic pressure field at an arbitrary point in space is derived for a wedge-shaped section of a spherical cap transducer using the spatial impulse response (SIR) method. For a spherical surface centered at the origin, a wedge shape is created by taking cuts in the X–Y and X–Z planes and removing the smallest surface component. Analytic expressions are derived for the SIR based on spatial location. The expressions utilize the SIR solutions for a spherical cap transducer [Arditi et al., Ultrason. Imaging 3, 37–61 (1981)] with additional terms added to account for the reduced surface area of the wedge. Results from the numerical model are compared to experimental measurements from a wedge transducer with an 8-cm outer diameter and 9-cm geometric focus. The experimental and theoretical −3-dB beamwidths agreed to within 10%±5%. The SIR model for a wedge-shaped transducer is easily extended to other spherically curved transducer geometries that consist of combinations of wedge sections and spherical caps. © 2003 Acoustical Society of America.
Show PACS
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.40.Yq Instrumentation and techniques for tests and measurement relating to shock and vibration, including vibration pickups, indicators, and generators, mechanical impedance
43.35.Wa Biological effects of ultrasound, ultrasonic tomography

The acoustic impedance of a circular orifice in grazing mean flow: Comparison with theory

Keith S. Peat, Jeong-Guon Ih, and Seong-Hyun Lee

J. Acoust. Soc. Am. Volume 114, Issue 6, pp. 3076-3086 (2003); (11 pages) | Cited 1 time

Online Publication Date: 02 Dec 2003

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It is well known that the presence of a grazing mean flow affects the acoustic impedance of an aperture, but the detailed nature and understanding of the influence is still unknown. In this paper, results from a recent theoretical analysis of the problem are compared with a new set of experimental results. The purpose is twofold. First, the experimental results are used to validate the theory. It is found that the theory predicts the resistance quite well, but not the reactance. Second, the theory is used to try and give some physical understanding to the experimental results. In particular, some scaling laws are confirmed, and it is also shown that measured negative resistance values are to be expected. They are not erroneous, as previously thought. Former sets of experimental data for this problem are notable for the amount of variation that they display. Thus, both the theory and the new experimental results are also compared with those earlier detailed results that most closely conform to the conditions assumed here, namely fully developed turbulent pipe flow of low Mach number past circular orifices. The main field of application is in flow ducts, in particular, flow through perforated tubes in exhaust mufflers. © 2003 Acoustical Society of America.
Show PACS
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.20.Tb Interaction of vibrating structures with surrounding medium
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