Research On High-resolution Acoustic Source Localization Algorithm For Rotating Sound Source

Noise pollution is one of the three major environmental problems.Rotating machinery noise is the main component among all kinds of mechanical noise,which is often closely related to the machinery fault and structural design.In addition,noise can seriously endanger human health.Microphone array is used to collect sound signals,based on which we can localize the sound source position and predict the radiation characteristic of the sound field,which helps to fundamentally control the noise source.Due to the Doppler effect and the mismatch of sound source position and the scanning grid point,the conventional sound source localization method cannot localize the rotating sound source.To solve the problem,this article focuses on the research of high-resolution localization of rotating sound source.The main contents are as follows:(1)Theoretical derivation and numerical simulation are carried out for the Doppler effect of the rotating acoustic source.Aiming at the main problem of rotating sound source localization,two rotating acoustic source beamforming methods are proposed: Phase Averaging Beamforming(PA-BF)and Time-domain De-doppler Beamforming(TD-BF).The advantage of PA-BF is that the procedure is easy to implement and all stationary acoustic source localization methods can be directly applied to this framework;the advantage of TD-BF is that it can eliminate the Doppler effect and can still work when sources move fast because the de-Doppler procedure works in the time domain.The subsequent numerical simulations examined the applicable scope of the two methods and verified the effectiveness and noise immunity of the proposed methods.(2)High-resolution algorithms are developed based on PA-BF and TD-BF.The classic deconvolution approach(Deconvolution Approach for the Mapping of Acoustic Sources,DAMAS)is introduced into the phase-averaged beamforming model to obtain a high-resolution localization algorithm named PA-DAMAS.Point spread function(PSF)is derived based on the model to characterize the resolution of acoustic source localization.In addition,this paper proposes an improved forward model of rotating acoustic source based on time-domain deDoppler Beamforming and equivalent source hypothesis.Two sparsity-based inverse methods are proposed to solve the inverse problem derived from the forward model.They are named as Least Absolute Shrinkage and Select Operator based on Time-domain De-doppler effect(TDLASSO)and Least Angle Regression based on Time-domain De-doppler effect(TD-LAR)respectively.The effectiveness of proposed methods is verified by numerical simulation.(3)Experimental research is carried out on the rotating acoustic source localization.In the anechoic room experiment,the proposed methods can successfully localize the single-frequency sound sources of the rotating Bluetooth speakers and the aerodynamic noise sources of the industrial fan.The sound source of the industrial fan is mainly located at the blade tip.In the fan production workshop,firstly,a variable-speed axial fan was tested and the results showed that the aerodynamic noise source of this fan was mainly located at the trailing edge of the blade,which might be vortex shedding noise.Furthermore,we can find that the intensity of the aerodynamic noise source gradually increases with the increase of the rotation speed,and the position of the sound source gradually moves outward along the radial direction of the fan with the increase of the center frequency.The test results of another axial flow fan showed that the proposed method can accurately identify the source of wingtip vortex noise caused by the vortex generator installed on the blade.The method of rotating acoustic source localization was studied in this paper.Highresolution localization methods for rotating acoustic source was developed based on the Beamforming energy propagation forward model.The effectiveness of the algorithm was verified through simulation and experiments.In addition,the proposed methods can accurately localize the aerodynamic noise sources of the axial fan and the wingtip vortex noise source generated by the vortex generators,which can provide certain technical support for the acoustic fault diagnose and low-noise design for the rotating machinery.