Sound absorber based on a sonic black hole and multi-layer micro-perforated panels

In order to achieve low-frequency and broadband sound absorption simultaneously, we propose a structure that combines a sonic black hole with multilayer micro-perforated panels. Firstly, we present finite element models for composite structures based on sonic black holes and micro-perforated panels and describe the sound absorption mechanism of the composite structure by comparing the sound absorption phenomena of micro-perforated panels with sonic black holes and micro-perforated panels with ordinary circular tubes. Secondly, the effects of the end coordinates of the sonic black hole, the number of panels and the parameters of the micro-perforated panels are discussed. Thirdly, the theoretical model of the proposed structure is developed using the transfer matrix method. Finally, the sound absorption test of the proposed structure is carried out using impedance tubes. The test results show that the sound absorption coefficient of the sample with a geometric length of 203 mm reaches 0.8 at 223 Hz and stabilizes above 0.9 at 398-1600 Hz. The sound absorber based on a sonic black hole and multi-layer micro-perforated panels has excellent sound absorption performance and has great research potential and application value.