Noise source localization on washing machines by conformal array technique and near field acoustic holography

The acoustic emission of a washing machine has been deeply studied by comparing three different techniques, which are: - conventional acoustic intensity, - planar near-field acoustic holography and - conformal array technique based on the Helmotz Equations Least Squares method. These techniques have been used to measure the front of a washing machine, i.e. the more critical side from the acoustic comfort point of view in the working environment. The acoustic intensity measurement has been taken as reference for the comparison of the two other techniques. The sound intensity probe has been scanned over a grid of several discrete positions and the acoustic intensity and pressure on the measurement plane have been determined. For both the conformal and planar near-field acoustic holography techniques an antenna of 30 microphones has been employed scanning over several positions in order to cover the entire washing machine front with a spatial resolution of 2.5 cm (maximum frequency 13720 Hz). Advantages and limitations of the noise source location techniques have been examined thoroughly.