Using suitable test equipment, it is possible to determine the acoustic signature of a vessel such as a submarine in port. Based on a measurement, the software generates a color map highlighting points of high acoustic emission, also known as "hot spots". In this way, the main sources having a direct impact on the vessel's discretion can be located, quantified, characterized and identified. Determining an acoustic signature easily and quickly in the hold can be a key step before a more costly validation at sea. Such an operation is typically of great interest after a maintenance operation to see if it has had an impact on this signature.
The methodology used is that of near-field acoustic holography (NAH). Nearfield Acoustic Holography). The first step is to acquire the acoustic pressure underwater and close to the hull. Given the typical shape of submarines, a cylindrical NAH method is essential. To this end, a cylindrical antenna comprising some twenty hydrophones is positioned close to the hull to measure underwater acoustic pressure. The propulsion system is started up but decoupled. In addition, all machinery likely to emit noise is put into operation. During this operation, the antenna is moved to different positions along the hull over the entire area to be mapped. The signals emitted by the hydrophones are acquired by the OROS instruments and analyzed by the dedicated OROS Underwater Holography software. The mappings are back-propagated on the hull by calculation, and scattered outwards to estimate the ship's far-field radiated noise. Finally, these maps are determined frequency by frequency. The OROS underwater holography solution is the only one currently available on the market.
Learn more: www.oros.com