Comparison Analysis and Optimization of Composite Micro-perforated Absorbers in Sound Absorption Bandwidth

Micro-perforated panel (MPP) absorber with a single uniform air cavity is regarded as a promising sound-absorbing structure; however, MPP absorption performance remains unfortunately limited due to the Helmholtz resonance mechanism, which results in more and more attention being placed on composite MPP absorbers. This study focuses on acoustic properties of different composite MPP absorbers, including three types of composite MPP absorbers which are coupled in serial, parallel and serial-parallel modes. Their mathematical models of the normal absorption coefficient are established by utilizing the acoustic electric analogy method. The single-cavity MPP absorber and three composite MPP absorbers are preliminarily designed to verify the equivalent circuit models and perform a pilot analysis of their sound absorption characteristics. Moreover, the particle swarm optimization algorithm is selected to optimize the absorbers so that optimal combination of structure parameters within a prescribed frequency range can be obtained. In addition, the absorbers are made based on the optimized parameters for experimental investigation. The results show that a wider absorption bandwidth may be achieved by composite MPP absorbers through introducing additional absorption peaks with reference to that for the conventional single-cavity MPP absorber, and there are more absorption peaks for the serial-parallel-coupled MPP absorber rather than the simply serial- or parallel-coupled MPP absorber so that better sound absorption effect may be achieved.