Holographic reconstruction of active sources in a three-dimensional enclosure

Abstract

This study proposes a method to identify active sources. The theory itself does not limit the application of the proposed method, but the main aim has been focused on finding the location of active noise sources and their strengths in an enclosure. The acoustic holography method can be applied to identify active sources, primary sources if one prefers to call them. However, it will depict all sources including imaginary sources, which one may call secondary sources, which are due to reflections on the walls of enclosure. In this study, an attempt has been made to distinguish these two different types of sources. First, boundaries are modeled by the inhomogeneous Robin boundary condition. It makes it possible to represent the boundaries as the combination of general ideal sources and passive boundaries; the ideal sources imply the primary sources, while the passive boundaries control the secondary sources. Second, this general boundary condition is combined with the holography method to reconstruct the strength of ideal sources. A technique for estimating surface admittance of passive boundaries is also proposed for a three-dimensional sound field by generalizing that for a duct.