Title: Sound absorption characteristics of underwater flexible micro-perforated sound absorption structures

Author(s): HOU Jiuxiao; ZHU Haichao; LIAO Jinlong; YUAN Suwei;

Affiliation(s): National Key Laboratory on Ship Vibration & Noise, Institute of Noise & Vibration, Naval University of Engineering

Abstract: A mathematical model for the micro-perforated panel in water medium is established using mode superposition method, and an equivalent circuit model is acquired based on electro-acoustic analogy method. Effects of the flexible micro-perforated panel（FMPP）and the flexible back panel（FBP）on normal incidence sound absorption coefficient are analyzed. Unlike micro-perforated panel in air medium, the underwater micro-perforated panel cannot achieve any satisfactory sound absorption effect due to insufficient structural impedance. To this end, a strengthened micro-perforated sound absorption structure is proposed. Theoretical results are verified in a water-filled impedance tube. Within the range from 20 Hz to 2,000 Hz the average absorption coefficient of the strengthened flexible micro-perforated panel are improved obviously. The absorption coefficient curve gradually approaches rigid micro-perforated panel as the bending stiffness increases. The flexible back panel can reduce the resonance frequency of the absorption curve and improve the low-frequency sound absorption performance.