Design and performance of ultra-broadband composite meta-absorber in the 200Hz-20kHz range

In this study, a composite meta-absorber with a flexible size is proposed, and a genetic algorithm is used to optimize the geometric dimensions under normal incidence and free field conditions. With an overall thickness of 0.2 m, the quasi-perfect sound absorption is achieved in the 200 Hz 20 kHz range. The sound pressure and sound intensity distributions inside the composite metaabsorber prove the incident sound wave is effectively localized inside the structure. Comparing the effective sound velocities in layers 1 and 10 with the sound velocity in air, it is possible to infer that the slow sound phenomenon is more pronounced at the bottom of THE composite metaabsorber, due to the different combinations of lateral plates and cavities. The coupling relationship between internal loss and radiation loss of the meta-absorber was revealed using the zero and pole method, proving the ultra-broadband and quasi-perfect sound absorption characteristics. Tests of the sound absorption coefficient in impedance tubes and reverberation chambers confirm the effective broadband sound absorption performance. The composite meta-absorber in this study can be directly used to reduce broadband noise. Moreover, it also provides ideas for the design of sound-absorbing metamaterials.