A lightweight low-frequency sound insulation membrane-type acoustic metamaterial

Kuan Lu,Nansha Gao,Jiu Hui Wu,Li Jing,Dong Guan

doi:10.1063/1.4942513

Kuan Lu, Nansha Gao + Show 3 more

Open Access

https://doi.org/10.1063/1.4942513

Copy DOI

Abstract

A novel membrane-type acoustic metamaterial with a high sound transmission loss (STL) at low frequencies (⩽500Hz) was designed and the mechanisms were investigated by using negative mass density theory. This metamaterial’s structure is like a sandwich with a thin (thickness=0.25mm) lightweight flexible rubber material within two layers of honeycomb cell plates. Negative mass density was demonstrated at frequencies below the first natural frequency, which results in the excellent low-frequency sound insulation. The effects of different structural parameters of the membrane on the sound-proofed performance at low frequencies were investigated by using finite element method (FEM). The numerical results show that, the STL can be modulated to higher value by changing the structural parameters, such as the membrane surface density, the unite cell film shape, and the membrane tension. The acoustic metamaterial proposed in this study could provide a potential application in the low-frequency noise insulation.

Highlights

Lightweight materials are often used in aerospace and automotive industry,[1] limited by the mass law, these materials have a fatal disadvantage
A novel membrane-type acoustic metamaterial with a high sound transmission loss (STL) at low frequencies ( 500Hz) was designed and the mechanisms were investigated by using negative mass density theory
Negative mass density was demonstrated at frequencies below the first natural frequency, which results in the excellent lowfrequency sound insulation

Summary

Introduction

Lightweight materials are often used in aerospace and automotive industry,[1] limited by the mass law, these materials have a fatal disadvantage. The concept of band-gap materials has been examined to deal with the difficult problems of noise insulation, especially the locally resonant crystal proposed by Liu et al.[2] Those materials showed a high STL at low frequencies, which is attributed to the negative effective elastic constants during the vibration. By attaching an adjustable small mass block onto the membrane with clamped boundaries, a negative mass density can be obtained at a specific frequency band, realizing the total reflection of low-frequency sound and breaking the mass law.[12] The effects of the membrane and mass properties on the transmission loss have been investigated,[13,14,15,16,17,18] and the sound insulation at low frequencies can be tuned by varying the acoustic metamaterial structure. Yao et al.[20] pointed out that a rectangular solid waveguide with clamped boundary

Methods

Results

Discussion

Conclusion