The Study Of MOEMS Acoustic Sensing Technology And Low Frequency Acoustic Transmission Properties

In modern battles on the sea, submarines face more challenges with the developing of gunship, and gunship has more advantages in the battles. In order to break the situation, countries in the world are developing water-to-air weapon systems. Our country has far-flung sea domain, and submarines play an very import role in defending sea domain. We must hold water-to-air weapon systems in order to protect our country, which leads to the vital significance to the security of our national and the world peace.In developing water-to-air weapon systems, one of the key problems is the submarine find gunship earlier and identifying and orientation. Based on national defence 863 item, MOEMS (Micro Optical electro mechanical system) acoustic sensor technology and low frequency acoustic transmit in the air and sea are studied. The main research content of full text is shown as follows:(1) Head of the MOEMS low frequency acoustic sensor is designed and simulated: based on basis principle of Fabry-Perot interferometer, loss of transmission, reflectivity and length of cavity of the MOEMS low frequency acoustic sensor are designed and simulated; mechanical and acoustic theories of micro-machine sense film are developed, and the micro-machine sense film is designed and simulated.(2) The micro-machine sense film is made. Because the film is so wafery that it is made difficultly, we made it through wet etching; we expatiate detailedly the craftwork flow of the micro-machine sense film; The loss of encapsulation is analysed and we encapsulated the sensor head; then, contrastive experiment between the MOEMS sensor and FOM sensor of Israel is done, and the sensitivity of MOEMS low frequency sensor is 50mV/Pa.(3) A fast field program (FFP) is developed to calculate the shallow water acoustic field excited by airborne low frequency source. And it is extended to handle the elastic bottom environment. We obtained the sound wave equations in homogenous and heterogeneous medium. Then we combined the appropriate boundary conditions of sound transmission, assumed the medium is horizontally stratified and its property does not change with range, by using the method of propagate matrix method, substitute function method and Fast Fourier Transform, finally we got the FFP algorithm for computing sound field through complicated mathematic operation.(4) Based on sea characteristics about acoustic spreading, we simulated the acoustic field in air and underwater with the low frequency source in the air. With these models, the transmission loss in shallow water, and the influence of the source height together with the lateral wave et al are studied.(5) The experiment in silencing poor are performed to study the acoustic field in blue sea for airborne low frequency (100Hz) source. The measured average transmission loss agree with the theoretical prediction well.To sum up, this thesis has design and production about the key equipment of low frequency sound detection buoy of warning system in air-sea background, this sample can detect low frequency signal, this lay the foundation of further study about sound detection buoy. Through the simulation of low frequency sound transmission characteristics in air-sea background, and the experiment in silencing poor, we conclude the theoretical basis about the array of acoustic sensors and sound detection.