Study On Sound Absorption Characteristic Of Locally Resonant Anechoic Coating

The research of vibration and noise reduction technology is an important guarantee for smooth underwater communication and safe operation,it is the most convenient and effective way to reduce vibration and noise by laying anechoic caoting outside the underwater vehicle shell.With the development of underwater active sonar towards low frequency,the low frequency acoustic absorption performance of anechoic caoting needs to be improved.In this paper,the locally resonant anechoic caoting is designed to improve the low frequency acoustic absorption performance by using the local resonance mechanism.The sound absorption performance and mechanism of locally resonant anechoic caoting were analyzed.The FEM numerical simulation model of phononic crystal plate type anechoic caoting and gradient type anechoic caoting were established,and the correctness of the numerical simulation model was verified by analytical method.After analysis,it can be concluded that the two locally resonant anechoic coating can effectively improve the low frequency sound absorption effect.The acoustic absorption mechanism of the two anechoic coating was analyzed by the absorption coefficient curve and displacement vector field.The synergistic effect of cavity resonance and scatterer resonance is the key to improve the acoustic absorption performance of phonon crystal plate type anechoic caoting.The gradient characteristics of the gradient anechoic coating intensifies the waveform conversion of acoustic wave in the anechoic coating,and the incident longitudinal wave is converted into shear wave which is more likely to dissipate in the rubber medium with large shear damping,which enhances the energy dissipation in the anechoic coating.In addition,the channel was established to realize the interactive operation of COMSOL link with MATLAB,and the geometric parameters of the phonon crystal plate type anechoic coating were optimized by the Genetic algorithm,so as to the sound absorption effect of 0Hz to 1000 Hz.By using FEM-BEM method,a numerical simulation model was established to calculate the acoustic scattering characteristics of single shell and shell with anechoic coating.The target strength(TS)frequency response curve and directivity curve of the shell model at different incidence directions within 1500 Hz were calculated.When the sound waves incident at 330°,the TS value increased with the increase of frequency.The scattering pressure of the shell surface near the source is greater than that of the side facing away from the source.The direction of large scattered sound pressure is mainly the direction of incidence and the direction of reflection when the sound waves are spread to the shell surface.Anechoic coating can effectively reduce the echo of the underwater shell in the direction of incidence and reflection,and reduce the intensity value of the target.With the increase of frequency,the sound absorption of the anechoic coating is gradually enhanced,and the reduction of TS is more obvious.