Acoustic based sensing of orthogonal radiating functions for three-dimensional noise sources: Background and experiments

This paper is concerned with the development of global, orthogonal, radiation patterns for 3D noise sources. Traditionally, sensing strategies for the active control of such sources is postulated on a vibration pattern and a set of radiation transfer functions. However, in practice not all noise sources are vibrational and accurate radiation functions (which may or may not be time invariant) are difficult to measure beyond the laboratory. The orthogonal basis functions developed in this work are based on a set of acoustic monopoles (arranged in a 3D array) described as multipoles, to decompose an independent set of radiating functions. The aim of the work is the design of practical acoustic sensing systems amendable to active noise control of large, complex, noise sources, or simply the characterisation and quantification of global radiation from such sources. Through experiments on a non-structural, 3D noise source, we examine the feasibility of the developed approach and compare and contrast the estimate of radiated power based on 2D and structural centric approaches.