Airborne sound characterisation by a dummy source approach

Abstract

A particular technique of experimental characterisation of a vibrating airborne sound source, the dummy source method, is explored. The dummy source is a simplified equivalent of the original source equipped with a number of drivers. The equivalence concerns both the sound radiation and the sound diffraction by the source. The dummy is identified from the measured sound of the running original source using an array of control microphones. Following the theoretical formulation of the method, a comparison of 2D sound fields produced by the original source and its dummy is carried out. Criteria regarding the number and positions of dummy source drivers and control microphones are set up, taking in account both the accuracy of sound reproduction by the dummy and the conditioning of measurements. The method is doubly validated by comparing the 3D sound fields produced by the original source and its dummy. First validation was done entirely by numerical simulation, while the second validation was done by comparing the measured sound of a real source with the computed sound radiated by the dummy. Reasonably good matching was achieved in both cases.