Rayleigh beam underwater metamaterial for low-frequency and broadband sound absorption

Abstract

Low-frequency and broadband underwater sound absorption has always been a primary industrial concern. Based on the coupling effect of Rayleigh beam vibration and Fabry-Perot resonance, a broadband underwater sound-absorbing metamaterial is proposed and experimentally achieved in this work. The Rayleigh beam vibration provides strong sound absorption at low frequencies ranging from 500 Hz to 3 kHz with a deep subwavelength configuration (1/100 of the wavelength at 500 Hz), while Fabry-Perot resonance works from 3 kHz to 10 kHz. Full-wave simulations and water-impedance tube tests are performed to demonstrate the sound absorbing mechanism. It is shown that the averaged sound absorption coefficient can arrive at 0.87 in a wide broadband range.