Acoustic Reverberation Measurements in the Depressurized Wave Basin

One method to determine the underwater radiated noise (URN) of the cavitating propeller of a ship is to perform model tests in a cavitation test facility. For proper analysis and interpretation of the measured noise levels, however, it is required to have a good understanding of the reverberation characteristics of the test facility.
In the EU FP7 project SONIC the reverberation characteristics of MARIN's Depressurized Wave Basin were determined through the use of calibrated sound sources. The influence of the concrete walls of the basin and the free surface on the measured sound was determined by means of impulse response measurements and direct response measurements. From these measurements, the reverberation radius is estimated, which is the radius below which the direct sound field is stronger than the sound field dueto the basin wall reflections. A method to correct for the influence of reflections from the free surface, the Lloyd's mirror effect, has also been studied. The measurement test set-up and the results of the experiments are presented in this paper.