An experimental investigation of planar nearfield acoustic holography using pressure and particle velocity measurements

Abstract

In the conventional nearfield acoustic holography （NAH）, only the pressure or particle velocity is used as the input quantity, and it cannot separate the waves from the two sides of the hologram surface. Therefore, all sources are assumed to be on one side of the hologram surface, i.e. the sound field is assumed to be free. This assumption limits the practical applications of NAH. In the NAH using pressure and particle velocity measurements, both pressure and particle velocity are used as the input quantities. By establishing and solving the coupling relationship on the hologram surface between the waves from the two sides of the hologram surface, the waves from the two sides can be separated. On the basis of the previous studies on sound field separation techniques and based on the Euler formula and the finite difference approximation technique, a new theoretical formula of NAH using pressure and particle velocity measurements is given, and then an experiment is performed to validate the method.