Research On Active Control Of Acoustic Wave Based On Metamaterial

Anechoic tile has been widely applied in submarine as acoustic stealth because of its superior acoustic properties. As sonar is developing in the direction of active detection and low frequency, it is necessary to increase the thickness of anechoic tile. However, submarine performance and installation of anechoic tile limit the increase of its thickness. Therefore, the control of broadband acoustic wave by anechoic tile is severely restricted. Due to its unique band structure and negative equivalent parameters for superior acoustic properties, acoustic metamaterials provide a new direction for broadband acoustic control. Active control technology has the characteristics of flexible structure, light quality and small volume, and it combines advantages both special acoustic characteristics of acoustic metamaterials and active control technology of acoustic wave. However, only a few of the work has been done on active acoustic control based on metamaterials. The existing mechanism mainly concentrates on the study of efficient negative parameters and extraordinary acoustic properties. Therefore, the active control technology of acoustic wave based on acoustic metamaterials was investigated theoretically and experimentally. The main content of the research includes:An active control model of acoustic metamaterials, which can be used to adjust the band structure distribution, was built based on transfer function method and LC resonance principle. The main structure of acoustic metamaterials, including piezoelectric material and fly ash/polyurea(FA/PU) composites, was built, at the same time, the gyrator circuit as active control module of acoustic metamaterial band was introduced. The influencing rule of parameters of the gyrator circuit on acoustic bandgap was obtained. The simulation analysis of acoustic metamaterial frequency distribution and absorption coefficient was done,the simulation results could be used for the optimization of the subsequent band distribution test and structure design.The active control method of the acoustic impedance for acoustic metamaterials were investigated using theoretical analysis and the simulation. An active control model of acoustic metamaterials, which can be used to adjust the acoustic impedance distribution, was built based on transfer function method. The method of tuning acoustic impedance by an external voltage was studied. The control program was written by Standard Commands for Programmable Instruments(SCPI), the real-time control system of acoustic impedance, which can be used to real-time incident acoustic wave detection, signal internal operation, acoustic impedance regulation, was developed. Finally, the simulation of acoustic impedance and the sound absorption coefficient of acoustic metamaterials was done.An experimental station, which can be used to make polyurea, was built. As damping layer structure, the fly ash/polyurea(FA/PU) composi tes are made of fly ash hollow spheres, which has the characteristics of small density and low cost. The acoustic metamaterials, which is composed of the fly ash/polyurea composites and piezoelectric ceramics was produced. The high-frequency and low-frequency acoustic detection system, which can be used to test wide-band acoustic performance, was established. The change rule and influencing factor of the band distribution and acoustic impedance, was analyzed. The effects of parameters of the external circui t and the external voltage on the acoustic performance of acoustic metamaterials was analyzed.