Optimal design of broadband quasi-perfect sound absorption of composite hybrid porous metamaterial using TLBO algorithm

In this study, the average sound absorption coefficient of a composite hybrid porous metamaterial (CHPM) structure was improved in the frequency range from 0 to 10 kHz by using the teaching–learning-based optimization algorithm when the geometric parameters (Layer spacing and lateral plate length) were regarded as optimization variables. The optimization results revealed that the CHPM exhibited an average sound absorption coefficient of 0.987. Three types of porous materials were used as matrix fillers, and the impedance of CHPM was found to almost perfectly matched with the surrounding air by using lateral plates of different lengths. The porous material suppresses the evanescent wave on the surface of CHPM and raises the sound absorption valley at each anti-resonance frequency, thus the reflection coefficient of the CHPM surface is extremely low. An effective medium model, transfer matrix method, and finite element method were jointly verified. The test results of the acoustic impedance tube proved that the optimized CHPM has a good sound absorption effect up to 1715 Hz. This proposed acoustic structure and optimization method would inspire more design ideas of new-type absorbers in ultra-broadband frequency range, and have potential applications in the field of industrial noise control and the construction of “quiet” cabin design.