Investigations of micro-perforated sound absorption structures for underwter usage

Micro-perforated sound absorption structures proposed by Professor Maa Dah- You have got abroad application on noise reductions and isolations in air.To our knowledge,however,there are no investigations and reports about their applications underwater.In this paper,the sound absorption formula of the same micro-perforated sound absorption structures underwater is derived from the corresponding theories in air. The conclusion that such structures cannot possess wide absorption is obtained.Then two modified micro-perforated panel sound absorption structures are proposed.Simulation results show that these structures have better sound absorption properties than those in air.The micro-perforated sound absorption structures designed and made by ourselves are tested in a standing-wave tube filled with water,and the experimental values of the sound absorption coefficient are in agreement with the theoretical values,which verify the theoretical analysis.