Effects of rough surface on frequency responses in non-anechoic tank

Abstract

The tank used for acoustical measurements should have sufficiently smooth frequency response curves. However, limited by number of modes, excitation and reception of sound field, the curves in non-anechoic tank fluctuate greatly, which causes unsatisfactory results. In this study, a method that reduces the fluctuation by rough surface is suggested. Numerical simulation by finite element computation is presented for sound field with rough surface. Simulation results reveal that there are more modes when the surface fluctuates randomly. Experiment results in non-anechoic tank with randomly fluctuant surface and in the static one are given. It is shown that smoother frequency response curves can be obtained with stronger modal behavior. The compared results between measurement and simulation show good agreements, which validates the effects of rough surface on frequency responses. This study provides a useful method for measuring the characteristics of narrowband signals in non-anechoic tank, and the applicability of the method is provided.The tank used for acoustical measurements should have sufficiently smooth frequency response curves. However, limited by number of modes, excitation and reception of sound field, the curves in non-anechoic tank fluctuate greatly, which causes unsatisfactory results. In this study, a method that reduces the fluctuation by rough surface is suggested. Numerical simulation by finite element computation is presented for sound field with rough surface. Simulation results reveal that there are more modes when the surface fluctuates randomly. Experiment results in non-anechoic tank with randomly fluctuant surface and in the static one are given. It is shown that smoother frequency response curves can be obtained with stronger modal behavior. The compared results between measurement and simulation show good agreements, which validates the effects of rough surface on frequency responses. This study provides a useful method for measuring the characteristics of narrowband signals in non-anechoic tank, and the applica...