The Study Of Sound Insulation Performance Of Membrane Acoustic Metamaterial

With the development of technology and human’s standard of living, deadening materials used in the industries of aerospace and construction are highlighted in their sound insulation and weight. Specially, insulation of low frequency sound is becoming increasingly importantDue to the restriction of mass-controlled law, the traditional sound insulation technology cannot meet the human’s need for low frequency sound. With the arising of acoustic metamaterials, the situation is changing. In this process, many investigations were focused on these materials and some progress has been made.In this thesis, an acoustic metamaterial was developed, consisting of rigid frames, a flexible film and an attaching mass. The band gap of the metamaterial was calculated theoretically. Finite element analysis of the sound transmission loss and verification by the experiments were also conducted.Firstly, the band structure and relation between band gap and frequency were obtained based on the classic band-gap characteristics of phononic crystals. The developed metamaterial was considered as a two-dimensional phononic crystal sheet. A program, based on the finite element theory and periodic condition, was written in the environment of MATLAB. It was seen that the propagation of elastic wave is suppressed severely in the band gaps frequency range, which will lead to the phenomenon of high reflection and low transmission. To verify this, finite element simulation was adopted to calculate the sound transmission loss of the multicell model. Results show no difference between two methods.In addition, the method of finite element simulation for calculating the sound transmission loss of thin-film acoustic metamaterials is introduced. Band gaps frequency range and sound transmission loss can be determined easily in these curves of sound transmission loss. In this regard, a series of finite element simulations were performed to investigate the effects of different materials on the sound transmission loss.In the final part of the thesis, by using standing wave pipe method, the sound transmission loss of thin-film acoustic metamaterials was measured. The standing wave pipe method is convenient, and provides a more realistic theoretical basis, since the wave propagates in a planar pattern. The measured results are consistent with the simulation results, verifying the correctness of finite element simulations.The acoustic metamaterial of membrane developed in this thesis has a wide potential application in areas such as vibration attenuation and sound insulation.