Study On Acoustic Wave Separation Method With Mini-sized Microphone Array Probe

What the existing on-line instruments for acoustic pressure measurement such as sound level meter measured is overall sound pressure,including interference noise.In the near-field acoutical holography(NAH)research area,sound wave separation can be utilized to keep measurement accuracy from interference noise source.However,the present methods of NAH based sound wave separation have limitations in the engineering practice,that is,double-layer acoustic pressure measurement array based separation method requires two layers parallel holographic measuring surfaces in the sound field and single-layer holographic surface based method ask for pressure and particle vibration velocity measuring on the measurement points.These two methods need to be implemented by hundreds of measurement signal.In order to overcome the limitations of complex implement and high-cost of existing sound wave separation methods,an acoustic wave separation technique based on mini-sized microphone array-probe was studied.The technique utilized the spherical wave superposition and approximation theory as the basis of separation method,and it can be applied to obtain acoustic pressure radiated from target in noise environment.To verify the feasibility of the technique,two mini-sized array-probes consist of four and five microphones were designed.In the sound field that contained interference noise,the separation of target source's acoustic wave can be achieved by processing complex pressure signal measured by array probe with acoustic wave separation method.The major work and achievement in the thesis as follows:The first chapter introduced background and significance of the research,then derivations of double-layer surface based method and single-layer surface based method are given,the limitations were discussed.The second chapter proposed a wave separation technique combined with mini-sized array probe based on theory of spherical wave functions superposition.Chapter three talked about numerical simulations of sound wave separation with sound field generated by two pulsating sources and the influence rules of measuring distance,source frequency,topological structure of array-probe,expansion number of basis functions on separation accuracy are discussed,respectively.Chapter four conducted experiments to verify the technique,two small speakers were taken as target source and interference source,respectively.Self-designed array probes consist of four or five microphones were utilized as measuring front-end,the experimental results in anechoic chamber showed that the sound wave separation technique can be used to restrain the interference noise on measurement of acoustic pressure radiated from target source.At last,the main research results in this paper had been summarized;the limitations of the studied technique and further research content were stated.