Study of the comparison of the methods of equivalent sources and boundary element methods for near-field acoustic holography

Valdivia, Nicolas; Williams, Earl G.

doi:10.1121/1.2359284

Cited by 93 publications

(45 citation statements)

References 18 publications

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“…2(c), the surface Γ s is decomposed into 828 points and 1414 triangles. The triangles forming the surface Γ s have an the average diameter length of 1 m and the approximate draft is 4.2 m. This definition of Γ s satisfies the parameters recommended in [12]. Fig.…”

Section: Numerical Experimentsmentioning

confidence: 91%

“…The spacing between sensors in Γ r is about 1 m, so that is the reason we require the spacing in Γ s to be approximately 1 m and the draft of Γ s to be 4.2 m (approximately 1 m away from Γ r ). As studied in more detail in [12], these conditions will guarantee that the ESM approach produce stable numerical representations of the electromagnetic radiation problem. Our objective for these experiments are two fold: first to investigate the global accuracy of reconstructed back-projected fields from the proposed NEH methodology.…”

Section: Numerical Experimentsmentioning

confidence: 99%

“…The BEM approach is well suited for radiation problems since the required accuracy of the solution justifies the expensive computations. In previous acoustic studies the authors [12] have shown that the equivalent sources method (ESM) is a valid approximation of BEM for near-field acoustic holography (NAH), i.e., the backpropagating problem of acoustics. It was determined that the error involved in the approximation given by ESM is of lesser magnitude than the measurement errors amplified in the reconstruction.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Underwater Electromagnetic Holography Imaging Techniques for Shallow Water Mediums

Valdivia¹,

Williams²,

Alqadah³

2017

PIER B

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Abstract-We propose an approach to characterize the AC underwater radiation produced by a ship over a shallow water medium using dipole sources distributed over an interior surface to the ship. The proposed approach relies on the accurate and efficient representation of dipole sources over the shallow water medium that characterizes the behavior of the electric or magnetic field. The approach is reduced to the solution of the resultant matrix system from the dipole representation. These systems are ill-posed, i.e., if the matrix systems are not solved by special regularization methods, the resultant solution will amplify the measurement noise. The regularization method applied is the least squares QR iterations combined with a new stopping rule that uses a numerical estimate of the measurement noise. Numerically generated data is used to study the validity of the different dipole representations. Finally, we validate our methodology using magnetic measurements that result from degaussing coils of a mid-size vessel.

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Section: Numerical Experimentsmentioning

confidence: 91%

Section: Numerical Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Underwater Electromagnetic Holography Imaging Techniques for Shallow Water Mediums

Valdivia¹,

Williams²,

Alqadah³

2017

PIER B

Self Cite

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show abstract

“…Then, a suitable propagator function is applied to the equivalent sources, in order to infer the velocity on the surface of the vibrating source. The computational cost of ESM is therefore highly reduced compared to IBEM [11]. Unfortunately, ESM is dependent on the number and positioning of the equivalent sources, which highly inftuence the accuracy of the estimation.…”

Section: Introductionmentioning

confidence: 99%

Dictionary-based Equivalent Source Method for Near-Field Acoustic Holography

Canclini

Varini

Antonacci

et al. 2017

2017 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

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In this paper, we propose a modification of the standard Equivalent Source Method (ESM) for Near-Field Acoustic Holography (NAH). As in EMS, we aim at modeling the acoustic pressure radiated from a vibrating object, and its surface velocity, as the joint effect of a set of equivalent sources located within or dose to the object itself. The estimation of the equivalent source strengths (weigths) comes from the solution of a highly ill-conditioned problem. Rather than solving this problem in the least-squares sense, we exploit the 3D model of the vibrating object, along with a rough estimate of its physical parameters, to restrict the space of the solutions. More specifically, we make use of Finite Element Analysis for populating a compressed dictionary of possible equivalent source weights. NAH is then approached by seeking a sparse linear combination of the entries of the dictionary. Experiments carried on a public database prove the effectiveness of the proposed technique, especially when the number of available microphones is limited, and in the presence of a significant level of measurement noise.

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“…In addition to the classical NAH technique based on spatial discrete Fourier transforms, 1-3 many alternative methods have been developed in the past years, e.g., the inverse boundary element method, [4][5][6] the statistically optimized method, 7,8 the Helmholtz equation least-squares method, 9,10 and the equivalent source method. [11][12][13] Among all these techniques NAH based on spatial Fourier transforms is the easiest to implement and also the most computationally efficient because of the use of the fast Fourier transform algorithm. However, the spatial Fourier transform method requires that the measurement aperture covers a large region where the level drops to a sufficiently low value near the edges in order to reduce truncation effects.…”

Section: Introductionmentioning

confidence: 99%

Patch near field acoustic holography based on particle velocity measurements

Zhang

Jacobsen²,

Bi³

et al. 2009

The Journal of the Acoustical Society of America

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Patch near field acoustic holography ͑PNAH͒ based on sound pressure measurements makes it possible to reconstruct the source field near a source by measuring the sound pressure at positions on a surface that is comparable in size to the source region of concern. Particle velocity is an alternative input quantity for NAH, and the advantage of using the normal component of the particle velocity rather than the sound pressure as the input of conventional spatial Fourier transform based NAH and as the input of the statistically optimized variant of NAH has recently been demonstrated. This paper examines the use of particle velocity as the input of PNAH. Because the particle velocity decays faster toward the edges of the measurement aperture than the pressure does and because the wave number ratio that enters into the inverse propagator from pressure to velocity amplifies high spatial frequencies, PNAH based on particle velocity measurements can give better results than the pressure-based PNAH with a reduced number of iterations. A simulation study, as well as an experiment carried out with a pressure-velocity sound intensity probe, demonstrates these findings.

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Study of the comparison of the methods of equivalent sources and boundary element methods for near-field acoustic holography

Cited by 93 publications

References 18 publications

Underwater Electromagnetic Holography Imaging Techniques for Shallow Water Mediums

Underwater Electromagnetic Holography Imaging Techniques for Shallow Water Mediums

Dictionary-based Equivalent Source Method for Near-Field Acoustic Holography

Patch near field acoustic holography based on particle velocity measurements

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