Acoustic signature measurements of a small submersible

Abstract

In an effort to characterize the acoustic signature of a small autonomous submersible, the FAU Ocean Explorer (OEX) class AUV (autonomous underwater vehicle), measurements of the acoustic source level were performed in a reverberant tank, with the submersible held stationary, with and without the propeller. For comparison, source level measurements were also performed off-shore at the South Florida Test Facility (NSWC-CD), in Ft. Lauderdale, FL and at the Acoustic Research Detachment (NSWC-CD), Lake Pend Oreille in Bayview, ID. The results of these measurements show that because of the relatively slow rotational speed of the propeller, the acoustic signature is low, although distinct features in the signature are discrete tones, which seem to be coming from the propeller. In fact measurements of the acoustic signature under power were difficult to obtain even in low background noise environments. For this reason, the reverberant tank measurements present a very effective approach provided broadband information is sufficient and directivity information is not necessary. Results from these three sets of measurements will be presented, together with an analysis of what are potentially the significant sources contributing to the acoustic signature. [Work supported by ONR.]