The Procedures of Mapped Radiation Mode Analysis Based Near-field Acoustic Holography

摘要

The derivatives of spherical basis functions can form a set of linearly independent velocity patterns which can span any velocity distributions on an arbitrary closed surface. They are termed as mapped radiation modes. It is proved that the field distribution pattern of the sound pressure generated by one mapped radiation mode on the surface of an exterior sphere is actually the spherical basis function with the same order and degree. The mapping relation between a vibrating surface and an exterior spherical surface is one-to-one. It suggests a promising way to rebuild the velocity on the surface of vibrating structure based on the mapped radiation mode. By setting up the microphone array at the integral points on an exterior spherical surface, the procedure to get the mapped radiation modes does not need inverse and regularization process. To get the participant coefficients of the mapped radiation mode accurately, an approach to determine the number of microphones and their locations on the spherical surface is proposed. Numerical simulations are present to validate advantages of applying the mapped radiation modes in the near-field acoustic holography (NAH).