Wavenumber domain regularization for near-field acoustic holography by means of modified filter functions and cut-off and slope iteration
2008 (English)In: Acta Acoustica united with Acustica, ISSN 1610-1928, Vol. 94, no 3, 339-348 p.Article in journal (Refereed) Published
Planar Near-field Acoustic Holography (PNAH) is an acoustic imaging method based on the inverse solution of the wave equation. Wavenumber domain low-pass filtering is an essential operation in the PNAH process. An increasingly higher wavenumber filter cut-off results in a "blow-up" of the inverse solution, which is a characteristic of an ill-posed problem. On the other hand, lower cut-off wavenumbers result in spatial acoustic data at very low resolution, where highly detailed information is discarded. Thus, an optimal solution for the cut-off wavenumber somewhere in between is needed. This paper introduces two modified filter functions, namely a modified exponential and a modified Tikhonov filter, that are specifically designed for application in PNAH and compares them with a number of more general applied filter functions. Regularization methods are introduced that exploit the k-space to obtain near-optimal low-pass filter parameter selection at high computational efficiency. These filter functions are discussed and their parameters are selected by k-space application of L-curve, Generalised Cross-Validation and the newly introduced and well-applicable Cut-Off and Slope iteration. Simulations of various sources show that the optimal regularization method is highly dependent on the type of source, the spatial distribution and measurement noise. Finally, a robust regularization strategy is proposed which automatically produces high quality results for a wide range of practical conditions.
Place, publisher, year, edition, pages
2008. Vol. 94, no 3, 339-348 p.
Acoustic holography, Acoustic imaging, Acoustics, Data recording, Dynamic loads, Holographic interferometry, Holography, Interferometry, Laser recording, Photoacoustic effect, Photonics, Signal filtering and prediction, Wave equations, Wave filters, Acoustic data, Blow-up, Cross validations, Cut-off, Filter functions, High-quality, Ill-posed problems, In-between, Inverse solutions, K-space, L curves, Low resolution, Low-pass filtering, Measurement noises, Near-field Acoustic Holography, Optimal regularization, Optimal solutions, Planar near-field, Regularization methods, Spatial distributions, Wave number domains, Wave numbers, Imaging techniques
Fluid Mechanics and Acoustics
IdentifiersURN: urn:nbn:se:kth:diva-66759DOI: 10.3813/AAA.918041ISI: 000257117200001OAI: oai:DiVA.org:kth-66759DiVA: diva2:498950
QC 201202132012-02-122012-01-272012-02-13Bibliographically approved