Research On Non-uniform Sampling And Sparse Sampling Of Near-field Acoustical Holography

Near-field acoustic holography is an advanced noise source identification and location technology.Because it can obtain abundant evanescent waves in the near-field range,near-field acoustic holography has a high resolution.However,with the gradual improvement of the requirements and standards of engineering technology for noise source location and identification,it is usually necessary to use a sufficient number of sampling points for measurement in near-field acoustic holography to meet the requirements of underwater noise source identification and location with high accuracy and resolution.As we all know,the underwater environment is complex and changeable,so too many underwater array hydrophone measuring points will produce some unpredictable environmental errors,which can make the reconstruction of near-field acoustic holography perhaps inaccurate.In this paper,a series of studies on the potential problems in the current application of near-field acoustic holography are conducted to further expand the engineering applications of acoustic holography.Firstly,understand the statistical optimal near-field acoustic holography from the principle,giving the conventional parameters of the method.Based on the nature of statistically optimal near-field acoustic holography,the method of non-uniform sampling in the wave number domain is proposed,and in analogy to the method of non-uniform sampling in the wave number domain,non-uniform sampling of the holographic surface is proposed,ultimately achieving an improvement in reconstruction accuracy and the effect of reducing the number of sampling points under the condition of ensuring reconstruction accuracy.The simulation results of different sampling conditions in holographic plane and wavenumber domain are compared through MATLAB,and the correctness and feasibility of the method are verified.Secondly,the principle and solution process of the equivalent source near-field acoustic holography and the theory of sparse sampling are derived and explained,as well as the specific method of how to apply the sparse sampling theory in the signal to the equivalent source nearfield technique Next,the superiority of the sparse sampling-based acoustic holography algorithm over conventional techniques is illustrated by comparing the sparse sampling-based equivalent source near-field acoustic holography algorithm.After that,the MATLAB simulation software was used to conduct a simulation study to determine the influence of parameters on the final results by changing the effective parameters to compare the reconstruction results.Finally,in this paper,simulation results of near-field acoustic holography for sparsely sampled equivalent sources are used to conduct underwater noise source localization experiments in an anechoic pool.Comparing the final results of the near-field acoustic holography with the traditional method in the anechoic pool with sparse sampling equivalent source method,it shows that the reconstruction effect is better based on sparse sampling and verifies its effectiveness and feasibility.