Contribution
Experimental Investigation of Acoustic Emissions from a Ship Hull
* Presenting author
Abstract:
The reduction of acoustic emissions of maritime vessels is gaining increasing attention. Since hydrophones cannot be used as external sensors during operation, alternative methods for measuring ship emissions are being explored.This study covers an experimental investigation of sound radiation from a ship’s hull. Initial experiments are conducted in a pier measurement on a KALKGRUND-class ship, using accelerometers and microphones inside the ship, as well as hydrophones deployed outside the ship in the water. The results demonstrate high coherence between microphones and hydrophones, indicating similar sound emission behavior into the air and into the water.Building on these findings, a second experimental setup is conducted using a scaled model of a patrol boat (1:8) in a laboratory environment (airborne sound). This setup investigates the possibility to reduce external acoustic emissions using internal microphones as error sensors. Noise reduction is achieved using an FxLMS algorithm, combined with inertial shakers mounted on the ship’s hull to actively cancel vibrations. Results show a tonal sound pressure reduction of 36 dB inside the ship and 20 dB reduction outside. These findings suggest that using internal error microphones can contribute to the reduction of a ship’s acoustic emissions.