An acoustic impedance structure consisting of perforated panel resonator and porous material for low-to-mid frequency sound absorption

Abstract

In this paper, an acoustic impedance compound structure composed of a perforated panel resonator (PPR) and porous sound absorbing material (PSAM) is designed to improve the sound absorption for low-to-mid frequency. The PPR component is an array cell of multiple Helmholtz resonators based on perforated panel arranged in parallel. By properly introducing a PSAM component that consists of porous material layers and rigid wall into the PPR component, a matched acoustic impedance appears at the coupling of the PPR and PSAM. Thus, the designed composite structure PPR-PSAM achieves an effective wide-band sound absorption through the effect of resonance dissipation by PPR and trapped energy by PSAM. An analytical model based on acoustic-electrical analogy is established to predict the sound absorption, and a finite element model is further proposed to demonstrate the sound absorption mechanism for the PPR-PSAM. Moreover, the influences of structural parameters on the sound absorption of the PPR-PSAM are discussed, and the sound absorption of the PPR-PSAM and the MPP (micro-perforated plate), MPP-PSAM are compared. The normal sound absorption coefficient measured by impedance tube is well agreed with the predicted results. In a limited space of 80 mm, the PPR-PSAM with low perforation rate has an average sound absorption coefficient of more than 0.89 from 200–1600 Hz.