Acoustic source property prediction based on near-field measurements in planar coordinate

Abstract

Near-field acoustical holography (NAH) can be used to predict the acoustical properties of noise sources by starting from measurements of near-field pressures. In particular, the sound pressure, particle velocity, and intensity can all be estimated on a source plane. In the present work, an equation relating acoustical source properties and the pressure radiated from a source is derived from the Kirchoff–Helmholtz integral equation and is here referred to as the inverse Rayleigh method. The inverse Rayleigh method reduces to the Rayleigh integral when the source is located on an infinite rigid baffle. However, the same equation can also be used to predict the acoustic properties of a source in a more general environment: i.e., without assuming the presence of an infinite rigid baffle. In this article, the inverse Rayleigh method is described and then its relative accuracy is compared with other procedures that can be used to predict source particle velocity from near-field pressure measurements on a planar hologram. By comparing the accuracy of the present NAH method with other procedures in the case of a large hologram, it was found that the inverse Rayleigh method is accurate and computationally efficient for predicting the source particle velocity from near-field pressure measurements both with and without a rigid baffle.