Measurement of directional scattering coefficients using near-field acoustic holography and spatial transformation of sound fields

Traditionally, conventional polar response measurements of scattering from objects have been done rising turntables or moving microphones and loudspeakers. In the current approach, near-field acoustic holography is used to measure the sound field above a scatterer. The scattered sound field is then spatially transformed to the desired distance and angle, corresponding to a certain angle relative to the normal of the surface. The method has been tested successfully on some scattering objects of interest, such as reflectors and diffusers in room acoustics. The method and assumptions are outlined. The method offers several advantages such as that the scattered sound field can be measured using a simple planar array and also that the scattered sound field can be predicted at various close distances to the scattering object.