title: Regularization for improving the deconvolution in real-time near-field acoustic holography.
abstract: Near-field acoustic holography is a measuring process for locating and characterizing stationary sound sources from measurements made by a microphone array in the near-field of the acoustic source plane. A technique called real-time near-field acoustic holography (RT-NAH) has been introduced to extend this method in the case of nonstationary sources. This technique is based on a formulation which describes the propagation of time-dependent sound pressure signals on a forward plane using a convolution product with an impulse response in the time-wavenumber domain. Thus the backward propagation of the pressure field is obtained by deconvolution. Taking the evanescent waves into account in RT-NAH improves the spatial resolution of the solution but makes the deconvolution problem "ill-posed" and often yields inappropriate solutions. The purpose of this paper is to focus on solving this deconvolution problem. Two deconvolution methods are compared: one uses a singular value decomposition and a standard Tikhonov regularization and the other one is based on optimum Wiener filtering. A simulation involving monopoles driven by nonstationary signals demonstrates, by means of objective indicators, the accuracy of the time-dependent reconstructed sound field. The results highlight the advantage of using regularization and particularly in the presence of measurement noise.
authors.affiliation: Laboratoire d'Acoustique de l'Université du Maine (LAUM Unité Mixte de Recherche-CNRS 6613), avenue O. Messiaen, 72085 Le Mans Cedex 09, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Paillasseur
authors.forename: Jean-Hugh
authors.initials: JH
authors.lastname: Thomas
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Pascal
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D003198:Computer Simulation; D005583:Fourier Analysis; D006696:Holography / Q000295:instrumentation; D008962:Models, Theoretical; D009038:Motion; D009716:Numerical Analysis, Computer-Assisted; D011312:Pressure; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013018:Sound Spectrography; D013997:Time Factors; D014159:Transducers