Forward Design Of The Helmholtz Resonator Type Acoustic Metamaterials

Acoustic metamaterials have good control effect on low and medium frequency noise due to their unique elastic band gap characteristics,which provide new theoretical method and approach for vehicle vibration and noise reduction.At present,various kinds of acoustic metamaterials were proposed mainly through reverse design,once the structural sizes and medium parameters of acoustic metamaterials were determined,the band gap characteristics were fixed,and it's difficult to control the elastic wave accurately.In this paper,the HR(Helmholtz resonator)type acoustic metamaterials were analyzed and a forward design method for HR type acoustic metamaterials was proposed.The main research work of this paper includes the following parts:Firstly,the theoretical basis of research on HR and acoustic metamaterials was introduced,including HR resonance theory,lattice theory,Bloch theorem and energy band theory,which lay a theoretical foundation for the future study of acoustic metamaterials.Secondly,the acoustic properties of one-dimensional and two-dimensional HR type acoustic metamaterials were calculated by using the multi-physical field simulation software COMSOL,The effects of key geometric parameters on the acoustic properties of the metamaterials were discussed,combined with the acoustic pressure cloud image inside the metamaterials,the mechanism of the local resonance band gap was explored.The defect states of acoustic metamaterials were studied,and the effects of different defect states in metamaterials were analyzed.Thirdly,according to the mechanism of local resonant band gap generation of HR type acoustic metamaterials,the calculation formula of HR resonance frequency was determined to calculate the initial band gap frequency,the applicable HR size range of the formula was discussed,and the calculation formula for the band gap cutoff frequency was derived.A mathematical model for the forward design of HR type acoustic metamaterials was established according to the calculation formulas of band gap start and cutoff frequencies.A forward design method for HR type acoustic metamaterials was designed,and a visual interface of forward design was developed through MATLAB GUI.Finally,two-dimensional HR type acoustic metamaterial plate was printed by 3D printer,an experimental platform to test the acoustic absorption coefficient and the acoustic absorption volume of the sample was set up,and the experimental results are compared with the simulation results.A HR type acoustic metamaterial periodic plate with different short tube sizes was designed and fabricated,and the acoustic absorption performance of the metamaterial plate with different short tube sizes was tested.In this paper,the acoustic properties of HR type acoustic metamaterials were studied,a forward design method was proposed,which provides a new idea for the structural design and engineering application of acoustic metamaterials,and makes the application of acoustic metamaterials in low and medium frequency noise reduction of vehicles more simple and efficient.