Research On Signal Direction Of Arrive Estimation And Surface Acoustic Radiation Contribution

The recognition of structures that contribute to far-field acoustic radiation has been a topic of concern in recent years.After the structure is known to have a large influence on the far field,proper control of this part of the structure can effectively reduce the far-field acoustic radiation of interest.This can not only reduce people's noise disturbance in life,but also hide from sound.The submarine's survivability is improved.Especially for underwater submarines,acoustic waves are the only way to transmit information underwater.Acoustic stealth technology is particularly important for their survivability.There are many applications for studying acoustic radiation on a vibrating surface.In recent years,researchers have paid special attention to sound source localization.The use of sound waves as a medium for underwater communication can help us detect,locate,track,and identify underwater targets.The array signal processing is introduced into the underwater acoustic field instead of the traditional single sensor,which can greatly reduce noise interference to the signal and can accurately locate the underwater far-field target.In this paper,the useful intensity and non-negative intensity methods are studied to identify the regions of the structure that contribute to far-field acoustic radiation,and an improved algorithm is proposed.In this paper,the array signal processing algorithms are used to locate the sound source and improve accordingly.The main tasks of this paper are as follows:(1)The algorithm of electromagnetic wave localization in air was introduced into the underwater sound source localization algorithm.Doppler effect and the influence of underwater channels were ignored.The MUSIC algorithm,smoothing algorithm,and ESPRIT algorithm were derived and extended to two-dimensional coherent signals.Processing algorithms that coexist with two-dimensional far-field and near-field signals.A method for noise reduction processing of the covariance matrix is proposed and verified by numerical simulation.The proposed method slightly improves the positioning accuracy.(2)Based on the theory of elastic mechanics and finite element theory,the finite element method was used to study the bending behavior of the Mindlin plate.The vibration mode calculation method was deduced.The analytical solution of the natural frequency of the simply supported plate with four sides was obtained.Establish a finite element model and compare the results obtained with the theoretical solution to verify the accuracy of the program being written.(3)Based on the supersonic intensity theory,two methods for identifying the contribution of the structure surface to the far field are obtained: useful intensity method and non-negative sound intensity method.The useful intensity method is given a reasonable explanation from the point of view of signal processing,and the results are divided into two parts that can be transmitted to the far field and that can not be propagated to the far field after the processing of the cutoff criterion,and a reasonable criterion for the determination of the cutoff criterion is proposed.The area where the surface of the structure contributes to the far field.The theory of non-negative intensity is deduced theoretically and the improved method is given.The improved method can better fit the results obtained by supersonic intensity method.Finally,the applicability of several methods is verified by using four-sided simple supported thin plate model to calculate the useful and non-negative acoustic intensities and the improved acoustic intensity and supersonic intensity results,and the improved method can obviously improve the recognition effect.