Low-frequency sound and vibration reduction of a metamaterial plate submerged in water

Abstract

Sound and vibration reduction of a metamaterial plate submerged in water is discussed theoretically and numerically. The modal superposition approach and Rayleigh integral technique are exploited in terms of the structural displacement and fluid pressure to investigate the low-frequency vibroacoustic characteristics of the underwater metamaterial plate and radiated sound field. Premised on the fluid-solid coupling mechanism, the acoustic band gaps generated by the underwater metamaterial plate to prevent the flexural waves propagation, are dramatically narrowed due to the extra fluid load, resulting in a reduction of the attached resonator's mass ratio over the host plate. Furthermore, from the theoretical formulae, extra sound radiation impedance can be observed to contribute to the plate's mechanical impedance owing to the presence of thick fluid, which greatly influences acoustic performance. As a result, it is concluded that in the low-frequency range, the vibroacoustic characteristic of the metamaterial plate is significantly affected by the ambient water. Results obtained from the theoretical analysis can provide guidelines on the design and optimization of acoustic metamaterials submerged in water to achieve prescribed acoustic properties.