185 / 2021-03-31 20:07:45

Equivalent source method based on ray wave function constrained by Dirac-delta function for near-field acoustic holography

Equivalent source method,near-field acoustic holography,ill-conditioned,ray wave function

Noise and vibration control

Near-field acoustic holography (NAH) based on equivalent source method (ESM) is a widely used sound field reconstruction technology in engineering. However, the transfer matrix formed by the ESM is usually ill-conditioned, which leads to a poor reconstruction stability. In most previous studies, the morbid of the transfer matrix is improved by optimizing the equivalent source location. However, the selection of the equivalent source locations is more complex and there are some limitations. Substituting the ray wave function with the traditional monopole spherical wave function, the transfer matrix can be dominant diagonally without changing the location of the equivalent source, and its condition number is reduced effectively. However, both ray wave function of the directional derivative of Green's function and ray wave function of orthogonal spherical wave source have larger side lobes and reverse main lobes, which will affect the dominant diagonal form of the transfer matrix. In order to solve this problem, this paper uses the directivity of Dirac-delta function to constrain the shape of ray wave function of orthogonal spherical wave source, and obtains a Dirac-delta constrained ray wave function with series summation form. This radiation wave function has the Dirac-delta function asymptotic property. It only has the required large main lobe in the main direction, and the side lobes in other directions are very small , so that the transfer matrix has a better dominant form in main diagonal. Numerical simulations has verified the effectiveness of proposed ray wave function in acoustic holography. The results show that the proposed ray wave function not only effectively reduces the condition number of transfer matrix, but also obtains more stable and accurate reconstruction results than the previous ray wave function in the case of the acoustic holography with noise .