An experimental setup for validation of the plane wave methods

Experiments are described which will serve to validate the, so called, plane wave decomposition(PWD); a method to measure in-situ absorption coefficients. A box (setup) has been build which consists of a cavity and a loudspeaker. The horizontal dimensions of the cavity can be altered, whereas, for simplicity, the height of the box has been designed to be sufficiently low. This is done to ensure a 2 dimensional sound field within the box. At various positions in the box, a number of closely spaced microphones have been used to measure the acoustic pressures within the cavity. Two methods have been implemented to derive the particle velocity from these measurements; one method is based on 2 microphones and one, a more accurate method, is based on 3 microphones. The results of the calculations of the experimental tests are compared with the results of the calculations of the simulated tests.