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Dispersion and scattering properties of a soft solid plate with solid cylindrical inclusions embedded in are theoretically and numerically reported in this work. The system is numerically analyzed considering both the vibroacoustic coupling and the presence of viscoelastic losses. In addition to the mechanical properties of the soft solid plate that allows the shift of the higher order Lamb modes to the low audible frequency domain, the presence of the inclusions introduces resonant and antiresonant phenomena in the subwavelength regime, leading to an elastic band-gap and a destructive modal interference in the soft solid plate able to interact with each other. These phenomena are used to design a system with strong transmission loss, breaking the mass law by 15 dB, and with subwavelength dimensions as the thickness is 32 times smaller than the equivalent wavelength in air. These performances are both computed and tested experimentally using a standard measuring process. • Soft solid material can be used to design low-frequency sound insulator. • Soft solid subwavelength plate with periodic inclusions overcomes the mass-law. • A destructive interference exists between the rigid body mode and a periodicity mode. • A band-gap and a destructive interference lead to a low acoustic transmission area. [ABSTRACT FROM AUTHOR]

Abstract: An acoustic metamaterial made of a two-dimensional (2D) periodic array of multi-resonant acoustic scatterers is analyzed both experimentally and theoretically. The building blocks consist of a combination of elastic beams of low-density polyethylene foam (LDPF) with cavities of known area. Elastic resonances of the beams and acoustic resonances of the cavities can be excited by sound producing several attenuation peaks in the low frequency range. Due to this behavior the periodic array with long wavelength multi-resonant structural units can be classified as a locally multi-resonant acoustic metamaterial (LMRAM) with strong dispersion of its effective properties.The results presented in this paper could be used to design effective tunable acoustic filters for the low frequency range. [Copyright &y& Elsevier]

An Acoustic Black Hole (ABH) in a one-dimensional (1D) beam is a passive vibration damping device based on a local reduction of the beam thickness attached to a thin layer of attenuating material. This work aims at revisiting the ABH effect by analysing the ABH trapped modes in the complex frequency plane. This analysis relies on an analytical model based on the one-dimensional thin beam theory and the transfer matrix method which assumes that the ABH termination is discretised by constant thickness piecewise elements. The model is validated with numerical simulations by the Finite Element Method. The reflection coefficients of several ABH terminations are studied. The results show that an ABH presents an infinite number of modes associated to an infinite number of poles and zeros of the reflection coefficient, the density and quality factor of which depend on the order of the ABH profile. By considering the ABH termination as an open lossy resonator, its damping efficiency results therefore from a balance between the energy leakage of each mode and its inherent losses, known as the critical coupling condition. In particular, the broadband absorption of the vibration energy is achieved for frequencies higher than that of the mode that is critically coupled. This type of analysis is used to interpret the ABH effect. It provides the losses needed to obtain the critical coupling condition, and is suitable for the optimisation of one-dimensional ABH terminations. [ABSTRACT FROM AUTHOR]