Noise source calibration in test tank

Noise level generated by engines and propellers of scientific manned or unmanned subsea vehicles has direct influence on on-board acoustic system performances. Noise measurements at sea are a very expensive operation. Tank measurements are more suited, but reverberation by the bottom, the walls and the surface alters the accuracy of the results. Measurement methods exist in reverberation chambers for aerial acoustics as well as electromagnetism. This communication shows that the transfer of the SABINE law to underwater acoustic measurements can be fully valid. Theory and experiments confirm that in the 15×10×6 meters concrete tank of IFREMER, an uniform reverberated field is present. It is thus possible to reach the tank absorption and the reverberation time. The analytic formula which is given allows the prediction of the radiated noise in free field, from the effective measurements done in the reverberated field and the tank reverberation characteristics. Experiments with calibrated noise sources show an accuracy of ±1.5 decibel