Search Results

The researches indicate that rational design of membrane-type acoustic metamaterial (MAM) can make it have a high sound transmission loss (STL) at the anti-resonant frequency. Based on the principle of local resonance of acoustic metamaterials, this paper studied the coupling interactions between sound field and vibration modes, and designed four lightweight MAM structural units with different distributed harmonic oscillators, and then the anti-resonant behaviors of different units within the low frequency were gradually analyzed. The regulation mechanism of continuous polymorphic anti-resonance modes on broadening STL bandwidth was further revealed, and the STL characteristics have been verified within the low-frequency range by numerical simulation and experiments. The results show that the design of a single cross-shaped resonator can increase the diversity of anti-resonance modes and eliminate the node-circular-type resonance mode, then ensure the wider STL bandwidth.

A flexible rebound-type acoustic metamaterial with high sound transmission loss (STL) at low frequency is proposed, which is composed of a flexible, light-weight membrane material and a sheet material - Ethylene Vinyl Acetate Copolymer (EVA) with uneven distributed circular holes. STL was analyzed by using both computer aided engineering (CAE) calculations and experimental verifications, which depict good results in the consistency between each other. An obvious sound insulation peak exists in the low frequency band, and the STL peak mechanism is the rebound-effect of the membrane surface, which is proved through finite element analysis (FEA) under single frequency excitation. Then the variation of the STL peak is studied by changing the structure parameters and material parameters of the metamaterial, providing a method to design the metamaterial with high sound insulation in a specified frequency range.

Acoustic performance of auto interiors is definitely important to control the NVH (noise, vibration, and harshness) performance inside a vehicle, and it is determined by the material parameters, such as density (ρ), thickness (d), open porosity (OP), airflow resistivity (σ), tortuosity (T), viscous characteristic length (VCL), thermal characteristic length (TCL), young's modulus, poisson's ratio, and damping coefficient. Firstly, by making different felt samples (of different surface density and thickness), the sound absorption performance and related parameters were obtained. Then the correlation between the parameters and the sound absorption coefficient (SAC) was summarized. Through this method, database of acoustic parameters and the corresponding SAC for porous materials can be established and sound package design and adjustment can be easily conducted based on the database.