Theoretical requirements and inverse design for broadband perfect absorption of low-frequency waterborne sound by ultrathin metasurface

Theoretical requirements and inverse design for broadband perfect absorption of low-frequency waterborne sound by ultrathin metasurface

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Abstract Effective absorption of low-frequency waterborne sound with subwavelength absorbers has always been a challenging work.In this paper, we derive two theoretical requirements for broadband perfect absorption of low-frequency waterborne sound by ultrathin acoustic metasurface under a finite-thickness steel plate followed by semi-infinite air.Based on the theoretical requirements, an acoustic metasurface, a rubber layer embedded periodically with cavities, is inversely designed to achieve perfect absorption at 500 Hz.The metasurface is as thin as 1% of the working fr5945 wavelength and maintains a substantially high absorptance over a relatively broad bandwidth.

The madelaine chocolate advent calendars perfect absorption peak is attributed to the overall resonance mode of the metasurface/steel plate system.Besides, high absorption can still be achieved even if the loss factor of the given rubber material cannot meet the ideal requirement.Finally, a strategy to utilize the inherent frequency-dependent characteristics of dynamic parameters of rubber material is suggested to achieve an ultra-broadband perfect absorption.When the frequency-dependent characteristics of the given rubber matrix cannot meet the theoretical requirements, a broadband super-absorption can still be realized by properly designing the frequency position of perfect absorption of the cavity-based metasurface.