Effect Comparative and Experimental Analysis of Diffraction Sound Field Caused by Impedance Sphere and Elastic Spherical Shell on Directivity of Vector Sensor

The directivity of acoustic vector sensor (AVS) will be distorted by the sound diffraction of the AVS carrier. A common AVS carrier in accordance with its acoustic characteristics can be approximately classified into three types: absolute soft air cavity, absolute rigid solid metal body and elastic shell filled with air. The focus of this paper is placed on the pressure and vibration velocity component of diffraction acoustic field caused by impedance boundary and elastic spherical boundary. Their mathematical expressions are deduced, and their directivity is also analyzed at different frequencies for different impedances. The results show that: for impedance boundary, its influences on directivity of pressure and vibration velocity is decided by the diffraction background term, and for the elastic shell boundary filled with air, the diffraction acoustic field can be seen as the sum of the diffraction acoustic field of rigid boundary and the radiated sound field of elastic vibration spherical shell boundary. When the frequency of the incident plane wave deviates from the resonance frequency of the elastic vibration shell, the diffraction acoustic field of the rigid boundary plays a major role, but when the frequency of the incident plane wave is close to the resonance frequency, the radiated sound field of the elastic vibration shell will hold the dominance. The experimental data are treated and the errors between the experimental results and the theoretical results are analyzed.