Investigation of scattering with acoustic holography.

The objective of this paper is to investigate sound scattering of a rigid sphere using the acoustic holography method. A piston source, which is vibrating sinusoidally, illuminates a sphere. The superimposed incident and scattered fields are measured in the near field of the sphere using acoustic holography. These two fields are decomposed in the wave-vector domain and, therefore, the scattered field is extracted. Numerical simulations are performed and the effect of various parameters is investigated. Specifically, the distance between two holography planes, the sampling rate, and the aperture size are investigated in the field separation technique. In addition, experimental studies were conducted inside an anechoic chamber with a baffled loudspeaker as a source and a cast-iron sphere as a scatterer. The experiments demonstrate the feasibility of the field separation technique based on two-plane acoustic holography. [Work supported by David Taylor Research Center.]