Experimental Application of High Precision K-space Filters and Stopping Rules for Fully Automated PNAH

• In general, inverse acoustic problems are ill-posed. Without any proper regularization actiontaken, noisy measurements result in an increasingly useless solution as the distance from themeasurement plane to the desired source grows. Two distinctive steps take place in the regularizationprocess for planar near-field acoustic holography (PNAH); first the low-pass filterfunction is defined and secondly a stopping rule is applied to determine the parameter settingsof said filter. A number of well-known and newly developed filter functions and stopping rulesare discussed and compared to one another, carefully listing the pros and cons. In acousticimaging practice it has proven to be very hard to determine the right filter for a certain casecombined with the automatic search for the near-optimal parameters. This paper presents anovel method that combines fitted filters for a broad number of possible experimental sourcescombined with highly efficient stopping rules, by taking advantage of k-space. Results basedon actual measurements demonstrate the effectiveness, applicability and precision of the fullyimplemented and automated regularization process for PNAH. Implementations include modificationsof Tikhonov, exponential and truncation low-pass filters, L-curve, Generalised Cross-Validation (GCV) and the novel Cut-Off and Slope (COS) parameter selection methods forPNAH.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Teknisk mekanik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Applied Mechanics (hsv//eng)

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