A thin meta-structure with multi-order resonance for underwater broadband sound absorption in low frequency

Abstract

In this paper, a thin meta-structure with several detuned multi-order micro-perforated panels with backing cavity (MPPB) for sound absorption is proposed, aiming to obtain broadband underwater sound absorption at low frequency. The MPPBs are designed with the method that inserting several micro-perforated panels into the origin backing cavity. In doing so, more sound absorption peaks can be obtained at higher frequencies, while the total thickness of the structure and the origin sound absorption peak are almost unchanged. The mechanism of multi-order resonance is analyzed in detail based on the electro-acoustic analogy and verified by the finite element simulation (FEA). Furthermore, the specific relationship between sound absorption performances and key parameters of MPPBs are investigated thoroughly. On this basis, by precisely adjusting the parameters of MPPBs and making them in a parallel arrangement, an 11-unit meta-structure with a thickness of only 75 mm is achieved, in which the maximum absorption coefficient of almost 100% and average absorption coefficient of 80% at 1380–3150 Hz.