Research On Algorithm Of Spheroidal Near-field Acoustic Holography

To the modeling of the outer layer of an underwater vehicle,nowadays we use the model of a cylinder.But the real shape of the vehicle is like a ‘water drop'.Compared to the cylindrical model adopted at present,the shape of the vehicle is nearer to a spheroid.So there are errors from the beginning of modeling.When the model of a cylinder is used to apply in the reconstruction of the acoustic field,only the acoustic pressure field of an imaginary sound source can be acquired.In the paper the algorithm of Fourier transforming in the near-field acoustic holography is studied and a new theory of spheroidal near-field acoustic holography is set up.Based on the Patch NAH algorithm of interpolation and extrapolation,more accurate results of the reconstruction can be obtained.So there is practical value and it is great significance for application.Firstly this paper introduces the theory of Fourier transforming in the near-field acoustic holography.Based on the principle of the conventional algorithm of the plane,cylinder and sphere,the correction of the algorithm is confirmed through the simulation of point acoustic source.This chapter makes preparations for the theory of spheroidal near-field acoustic holography.Secondly,this paper sets up a spheroidal coordinate.According to the physical meaning of the coordinate,the form of Helmholtz equation is obtained.After applying the method of separating variables,we get the analytic solution of the equation.Through the mathematical simulation and mathematical analysis,we get the properties of the solution.Thirdly,based on the basic principles of near-field holography and analytic solution of Helmholtz equation,this paper sets up the theory of spheroidal near-field holography.Through the simulation of single-point source and double-point source,the correction of the algorithm is confirmed.This paper also studies conventional PGA methods of Patch near-field acoustic holography.After applying it to spheroidal coordinate,we set up spheroidal PGA algorithm of interpolation and extrapolation.By comparison of mathematical simulation,the results show the superiority of the combinatorial algorithm.In this article the algorithm of interpolation and extrapolation is applied to the spheroidal coordinate system.In the combinatorial algorithm not only does it achieve the optimization ofthe original model,but also it optimizes the conventional algorithm.It improves the accuracy of reconstruction.