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Feb 2012

Volume 131, Issue 2, pp. EL87-1825

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A wave field synthesis approach to reproduction of spatially correlated sound fields

Alain Berry, Rokhiya Dia, and Olivier Robin

J. Acoust. Soc. Am. Volume 131, Issue 2, pp. 1226-1239 (2012); (14 pages) | Cited 3 times

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This article discusses an open-loop wave field synthesis (WFS) approach for the reproduction of spatially correlated sound fields. The main application concerns laboratory reproduction of turbulent boundary layer wall pressure on aircraft fuselages and measurement of their sound transmission loss. The problem configuration involves reconstruction of random sound pressure distributions on a planar reproduction surface using a planar array of reproduction monopoles parallel to the reproduction plane. In this paper, the WFS formulation is extended to sound fields with imposed time and spatial correlation properties (or equivalently imposed cross-spectral density in the frequency and wave number domains). Numerical examples are presented for the reproduction of a propagating plane wave, diffuse acoustic field and wall pressure in subsonic or supersonic turbulent boundary layers. The reproduction accuracy is examined in terms of the size of the source plane and reproduction plane, their separation, and the number of reproduction sources required per acoustic wavelength. While the reproduction approach cannot reconstruct sub-wavelength correlation scales of subsonic turbulent boundary layers, it effectively reconstructs correlation scales larger than the acoustic wavelength, making it appropriate for diffuse acoustic field and supersonic turbulent layers.
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43.60.Fg Acoustic array systems and processing, beam-forming
43.38.Md Sound recording and reproducing systems, general concepts
43.40.Sk Inverse problems in structural acoustics and vibration
43.60.Cg Statistical properties of signals and noise

Maximum likelihood estimation of direction of arrival using an acoustic vector-sensor

Dovid Levin, Emanuël A. P. Habets, and Sharon Gannot

J. Acoust. Soc. Am. Volume 131, Issue 2, pp. 1240-1248 (2012); (9 pages) | Cited 2 times

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A vector-sensor consisting of a monopole sensor collocated with orthogonally oriented dipole sensors is used for direction of arrival (DOA) estimation in the presence of an isotropic noise-field or internal device noise. A maximum likelihood (ML) DOA estimator is derived and subsequently shown to be a special case of DOA estimation by means of a search for the direction of maximum steered response power (SRP). The problem of SRP maximization with respect to a vector-sensor can be solved with a computationally inexpensive algorithm. The ML estimator achieves asymptotic efficiency and thus outperforms existing estimators with respect to the mean square angular error (MSAE) measure. The beampattern associated with the ML estimator is shown to be identical to that used by the minimum power distortionless response beamformer for the purpose of signal enhancement.
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43.60.Jn Source localization and parameter estimation
43.60.Fg Acoustic array systems and processing, beam-forming

Fast implementation of sparse iterative covariance-based estimation for source localization

Qilin Zhang, Habti Abeida, Ming Xue, William Rowe, and Jian Li

J. Acoust. Soc. Am. Volume 131, Issue 2, pp. 1249-1259 (2012); (11 pages)

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Fast implementations of the sparse iterative covariance-based estimation (SPICE) algorithm are presented for source localization with a uniform linear array (ULA). SPICE is a robust, user parameter-free, high-resolution, iterative, and globally convergent estimation algorithm for array processing. SPICE offers superior resolution and lower sidelobe levels for source localization compared to the conventional delay-and-sum beamforming method; however, a traditional SPICE implementation has a higher computational complexity (which is exacerbated in higher dimensional data). It is shown that the computational complexity of the SPICE algorithm can be mitigated by exploiting the Toeplitz structure of the array output covariance matrix using Gohberg–Semencul factorization. The SPICE algorithm is also extended to the acoustic vector-sensor ULA scenario with a specific nonuniform white noise assumption, and the fast implementation is developed based on the block Toeplitz properties of the array output covariance matrix. Finally, numerical simulations illustrate the computational gains of the proposed methods.
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43.60.Jn Source localization and parameter estimation
43.60.Fg Acoustic array systems and processing, beam-forming
43.60.Gk Space-time signal processing, other than matched field processing

An equivalent source technique for recovering the free sound field in a noisy environment

Chuan-Xing Bi and J. Stuart Bolton

J. Acoust. Soc. Am. Volume 131, Issue 2, pp. 1260-1270 (2012); (11 pages) | Cited 1 time

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In previous studies, a sound field separation technique based on the equivalent source method (ESM) was successfully applied to separate the incoming and outgoing fields composing a non-free field. However, if the incoming wave is scattered by the source surface, the outgoing field is not the field that would be generated by the source in a free field. The object of the present work was to provide an equivalent source technique that allows the recovery of that free field in a noisy environment. In this approach, the incoming and outgoing fields, including the scattered and directly radiated fields on the measurement surface, are separated to obtain the free-field pressure that would be radiated by the source in an anechoic environment. The recovered free-field pressure is then used to reconstruct the whole free field of the source by using near-field acoustical holography based on the ESM, which makes the results equivalent to those that could be obtained from a free-field measurement. A theoretical description of the technique is given first, and then three numerical cases are investigated to demonstrate the ability of the proposed method.
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43.60.Pt Signal processing techniques for acoustic inverse problems
43.60.Sx Acoustic holography
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods

Sparsity driven ultrasound imaging

Ahmet Tuysuzoglu, Jonathan M. Kracht, Robin O. Cleveland, Müjdat C¸etin, and W. Clem Karl

J. Acoust. Soc. Am. Volume 131, Issue 2, pp. 1271-1281 (2012); (11 pages)

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An image formation framework for ultrasound imaging from synthetic transducer arrays based on sparsity-driven regularization functionals using single-frequency Fourier domain data is proposed. The framework involves the use of a physics-based forward model of the ultrasound observation process, the formulation of image formation as the solution of an associated optimization problem, and the solution of that problem through efficient numerical algorithms. The sparsity-driven, model-based approach estimates a complex-valued reflectivity field and preserves physical features in the scene while suppressing spurious artifacts. It also provides robust reconstructions in the case of sparse and reduced observation apertures. The effectiveness of the proposed imaging strategy is demonstrated using experimental data.
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43.60.Pt Signal processing techniques for acoustic inverse problems
43.60.Uv Model-based signal processing
43.60.Fg Acoustic array systems and processing, beam-forming
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