Determination of the directivity of a planar noise source by means of near field acoustical holography, 1: theoretical background

Abstract

The theoretical basis of the application of the technique of near field acoustical holography to the measurement of the directivity of a planar noise source is discussed. Problems arising from the application of the techniques are identified. These arise primarily from the need to work with sampled data over a limited aperture size, as opposed to the continuous function assumed in deriving the basic theory. Techniques for overcoming these problems are suggested including the use of data windows and k-space filtering. A particular problem that is identified is the need to generate data points in k-space other than those corresponding to actual samples. Techniques based upon interpolation in k-space are proposed in order to overcome this problem.