Low frequency broadband sound absorber via multi-layer perforated plate with through-back cavity

Acoustic porous materials are generally applied to noise control, but they are ineffective in the low-frequency band, and cannot break through the difficulty of efficient sound absorption at low-frequency. Perforated plate acoustic absorber has strong acoustic absorption ability at resonance frequency. However, the ordinary perforated plate is limited in bandwidth, and needs to be combined with porous acoustic absorber or cavity to improve the performance. Microperforated plates can achieve good acoustic absorption, but the strong dispersion characteristics limit their bandwidth. In order to broaden the bandwidth, in this research, a new broadband sound absorber structure is proposed. A direct coupling regulation design of connecting the back cavity is introduced into the structure. Its acoustic performance is verified by simulation. The external field distribution is calculated in the diffuse scattering acoustic field, which realizes the near-perfect broadband acoustic absorption effect in the frequency band of 380-2000 Hz. The average sound absorption coefficient reaches 0.91.