The radiation efficiency grouping of free-space acoustic radiation modes

Cunefare, Kenneth A.; Currey, M. Noelle; Johnson, Marty; Elliott, Stephen J.

doi:10.1121/1.1323236

Cited by 46 publications

(17 citation statements)

References 26 publications

(38 reference statements)

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“…In Fig. 4, the grouping behavior of the exterior radiation mode eigenvalues can be observed as described by Cunefare et al 15 and by Wu et al 40 and as obtained for the circle in Sec. 5.1, which is a pure exterior acoustic problem without holes or chambers with interior modes.…”

Section: Influence Of Infinite Elements On Radiation Modesmentioning

confidence: 61%

“…3. The grouping behavior of ARM eigenvalues or radiation efficiencies in terms of acoustical multipoles has already been presented by Cunefare et al 15 for three-dimensional problems and by Wu et al 40 …”

Section: Circlementioning

confidence: 98%

“…They are orthogonal with respect to the product (15) and depend on the choice of the parameters α and β. The product of trial and test functions in the variational statement in the two-dimensional case is of the same form as the orthogonality relationship of the Jacobi polynomials when α = 1 and β = 0…”

Section: Jacobi Polynomialsmentioning

confidence: 99%

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Infinite Elements and Their Influence on Normal and Radiation Modes in Exterior Acoustics

Moheit

Marburg

2017

J. Comp. Acous.

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Acoustic radiation modes (ARMs) and normal modes (NMs) are calculated at the surface of a fluid-filled domain around a solid structure and inside the domain, respectively. In order to compute the exterior acoustic problem and modes, both the finite element method (FEM) and the infinite element method (IFEM) are applied. More accurate results can be obtained by using finer meshes in the FEM or higher-order radial interpolation polynomials in the IFEM, which causes additional degrees of freedom (DOF). As such, more computational cost is required. For this reason, knowledge about convergence behavior of the modes for different mesh cases is desirable, and is the aim of this paper. It is shown that the acoustic impedance matrix for the calculation of the radiation modes can be also constructed from the system matrices of finite and infinite elements instead of boundary element matrices, as is usually done. Grouping behavior of the eigenvalues of the radiation modes can be observed. Finally, both kinds of modes in exterior acoustics are compared in the example of the cross-section of a recorder in air. When the number of DOF is increased by using higher-order radial interpolation polynomials, different eigenvalue convergences can be observed for interpolation polynomials of even and odd order.

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Section: Influence Of Infinite Elements On Radiation Modesmentioning

confidence: 61%

Section: Circlementioning

confidence: 98%

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Infinite Elements and Their Influence on Normal and Radiation Modes in Exterior Acoustics

Moheit

Marburg

2017

J. Comp. Acous.

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“…23 Therefore, unlike the spherical harmonics, the ARMs are frequency dependent, which might lead to impractical spatial filters as far as loudspeaker arrays for directivity control are concerned. However, simulation results have indicated that the ARMs of the PSLs do not depend on frequency, 13,26 although a mathematical proof has not been presented so far.…”

Section: Introductionmentioning

confidence: 99%

“…This leads to basis elements that radiate sound energy independently and decay with distance at very different rates in the near field, such as the spherical harmonics and the ARMs. [22][23][24] Hence, the regularization technique generally adopted consists in discarding the eigenvectors (or eigenfunctions) associated to very small eigenvalues, which arise from strongly decaying waves, especially at low frequencies.…”

Section: Introductionmentioning

confidence: 99%

On the acoustic radiation modes of compact regular polyhedral arrays of independent loudspeakers

Pasqual¹,

Martin²

2011

The Journal of the Acoustical Society of America

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Compact spherical loudspeaker arrays can be used to provide control over their directivity pattern. Usually, this is made by adjusting the gains of preprogrammed spatial filters corresponding to a finite set of spherical harmonics, or to the acoustic radiation modes of the loudspeaker array. Unlike the former, the latter are closely related to the radiation efficiency of the source and span the subspace of the directivities it can produce. However, the radiation modes depend on frequency for arbitrary distributions of transducers on the sphere, which yields complex directivity filters. This work focuses on the most common loudspeaker array configurations, those following the regular shape of the Platonic solids. It is shown that the radiation modes of these sources are frequency independent, and simple algebraic expressions are derived for their radiation efficiencies. In addition, since such modes are vibration patterns driven by electrical signals, the transduction mechanism of compact multichannel sources is also investigated, which is an important issue, especially if the transducers interact inside a shared cabinet. For Platonic solid loudspeakers, it is shown that the common enclosure does not lead to directivity filters that depend on frequency.

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Developments in structural-acoustic optimization for passive noise control

Marburg

2002

ARCO

157

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Low noise constructions receive more and more attention in highly industrialized countries. Consequently, decrease of noise radiation challenges a growing community of engineers. One of the most efficient techniques for finding quiet structures consists in numerical optimization. Herein, we consider structural-acoustic optimization understood as an (iterative) minimum search of a specified objective (or cost) function by modifying certain design variables. Obviously, a coupled problem must be solved to evaluate the objective function. In this paper, we will start with a review of structural and acoustic analysis techniques using numerical methods like the finite-and/or the boundary-element method. This is followed by a survey of techniques for structural-acoustic coupling. We will then discuss objective functions. Often, the average sound pressure at one or a few points in a frequency interval accounts for the objective function for interior problems, whereas the average sound power is mostly used for external problems. The analysis part will be completed by review of sensitivity analysis and special techniques. We will then discuss applications of structuralacoustic optimization. Starting with a review of related work in pure structural optimization and in pure acoustic optimization, we will categorize the problems of optimization in structural acoustics. A suitable distinction consists in academic and more applied examples. Academic examples include simple structures like beams, rectangular or circular plates and boxes; real industrial applications consider problems like that of a fuselage, bells, loudspeaker diaphragms and components of vehicle structures. Various different types of variables are used as design parameters_ Quite often, locally defined plate or shell thickness or discrete point masses are chosen. Furthermore, all kinds of structural material parameters, beam cross sections, spring characteristics and shell geometry account for suitable design modifications. This is followed by a listing of constraints that have been applied. After that, we will discuss strategies of optimization. Starting with a formulation of the optimization problem we review aspects of multiobjective optimization, approximation concepts and optimization methods in general. In a final chapter, results are categorized and discussed. Very often, quite large decreases of noise radiation have been reported. However, even small gains should be highly appreciated in some cases of certain support conditious, complexity of simulation model and large frequency ranges. Optimization outcomes are categorized with respect to objective functions, optimization methods, variables and groups of problems, the latter with particular focus on industrial applications. More specifically, a close-up look at vehicle panel shell geometry optimization is presented. Review of results is completed with a section on experimental validation of optimization gains. The conclusions bring together a number of open problems in the field.Obviously, the (non-Her...

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The radiation efficiency grouping of free-space acoustic radiation modes

Cited by 46 publications

References 26 publications

Infinite Elements and Their Influence on Normal and Radiation Modes in Exterior Acoustics

Infinite Elements and Their Influence on Normal and Radiation Modes in Exterior Acoustics

On the acoustic radiation modes of compact regular polyhedral arrays of independent loudspeakers

Developments in structural-acoustic optimization for passive noise control

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