Study On Noise Source Localization Based On Beamfroming And Wave Superposition Method

Accurate noise source localization is the precondition of noise and vibration control of machine.The location and intensity of the noise source can be figured out by beamforming through non-contact measurement,however,the results of beamforming were affected seriously by the side-lobe phenomenon and beamforming can't identify the Z coordinate of noise source.The above defects of beamforming were studied and analyzed in this paper,especially,the "Shrinkage phenomenon" of beamforming was founded during the identify experiments of noise sources with different Z coordinate,then the principle of Shrinkage was assumed,analyzed and verified successfully.The improve method to solve the above three defects of beamforming was proposed based on wave superposition method and genetic algorithm in this paper.Simulation and experiment results show that the improve method can make the performance of beamforming better successfully.The detail research work mainly includes:(1)The side-lobe phenomenon and difficult of Z coordinate identification were studied firstly,and the "Shrinkage" was founded during the Z coordinate identification.Shrinkage means that the identify result of beamforming moves to reconstruction plane center gradually as the Z coordinate of noise source being larger and larger.At the same time,it was assumed that the beamforming identify result is intersection of reconstruction plane and the line segment between noise source and geometric center of microphone array.This assumption turns out to be correct by groups of simulation experiments.(2)Study of noise source localization based on wave superposition method were carried out,and the simulation result was compared with beamforming.The comparison shows that noise source localization based on wave superposition method can suppress the side-lobe phenomenon successfully,but needs too much measurement work and costs a lot.(3)The improve method was proposed based on wave superposition method and genetic algorithm to eliminate the side-lobe phenomenon,shrinkage phenomenon and figure out the Z coordinate of noise source.This improve method needs pre-localization by beamforming,then set equivalent sources and make the sound pressure reconstruction error of microphone array as the evaluation index,search the location and intensity of noise source based on wave superposition method and genetic method finally.This improve algorithm was translated into MATLAB code and proved to be effective by simulation experiments.(4)The improve method is further proved to be effective by noise source localization experiments which were carried out in a semi-anechoic room and loudspeakers as noise sources.Then the noise sources of side of diesel were localized by the above improve method.