Measurement of structural intensity using patch near-field acoustical holography

Abstract

Measurement of power flow in a structure, called the structural intensity (SI), is essential for vibration control and noise reduction. The near-field acoustical holography (NAH)-based measurement method is suitable to analyze the interrelationship between SI and acoustic intensity (AI) because NAH-based methods provide measurements of SI and AI simultaneously. Use of NAH requires the measurement of a pressure field over a complete surface located exterior to the structure. Therefore, if the measurement aperture is smaller than the structure, reconstructed results from the pressure on the finite aperture are seriously contaminated. This finite aperture effect prevents implementation of this NAH-based method on an actual large-scale structure such as a ship. Patch NAH and regularization method for SI measurement are applied to overcome this difficulty. This method enables implementation of the NAH-based SI measurement method in a large-scale structure. The effectiveness of this method is demonstrated by experiment.