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Regularization method for measurement of structural intensity using nearfield acoustical holography
Kenji Saijyou1, Chiaki Okawara
1Fifth Research Center, Technical R & D Institute, Japan Defense Agency, 3-13-1 Nagase, Yokosuka, 239-0826, Japan. saijyou-kenji@jcom.home.ne.jp
Abstract:
The regularization method for measurement of structural intensity using nearfield acoustical holography is proposed. Spatial derivatives of normal displacement are necessary to obtain the structural intensity. The derivative operations amplify high-wave-number components of measurement noise. Therefore, the estimation of an appropriate wave-number filter is crucial for implementation of the measurement of structural intensity. In conventional methods, this wave-number filter is determined from the flexural wavelength. And the same wave-number filter is applied to obtain all spatial derivatives. As a result, structural intensity obtained from the pressure hologram, whose signal-to-noise ratio is low, is seriously contaminated by the noise. To overcome this difficulty, regularization theory is applied to determine the appropriate wave-number filter for each order of derivatives. The effectiveness of the proposed method is demonstrated by experiments.
