Modelling correlated and uncorrelated sound sources

Abstract

In this study the relationship between near-field sound intensity and normal surface velocity, relating to a sound source, was investigated. Predictive techniques will aid with development of an integrated design tool. Correlated and uncorrelated sound sources in the frequency range of 63Hz to 1000Hz were examined through an experimental and numerical activity. The sound source consisted of 8 independent loudspeakers in an enclosure. Sound intensity measurements in the near-field of the source were measured over an enclosed surface. Substitution Monopole Technique (SMT) for both correlated and uncorrelated sources was used to compute normal monopolar surface velocities from measured near-field sound intensity levels. The calculated normal monopolar surface velocities were used as boundary conditions to drive an acoustic Indirect Boundary Element Model (IBEM) of the sound source. From 63Hz to 400Hz the correlated SMT was accurate within +/-2dB but under predicts above this frequency. The uncorrelated SMT using pesudo random phasing was accurate within +/-3dB across the frequency range. © 2008 Springer-Verlag London Limited.