Low frequency acoustic radiation of cylindrical shells in water

Abstract

The assessment of sound pressure levels generated by submerged structures is part of problems regarding underwater noise pollution. The growing number of offshore constructions related to energy generation by wind farms increases the importance of these studies. The understanding of physical mechanisms responsible for this radiation should allow us to reduce the noise by refining the construction of structures. The object of the present work is the study of underwater acoustic radiation of tube vibrations. The results presented were obtained on two stainless steel tubes. These tubes are placed vertically into water. The vibrations are generated by a shock obtained using a hammer with a force sensor hitting the tube on the emerged part. The vibrations of the tube placed in the air and in water are measured using accelerometers. The influence of water on the modes of resonances observed is then highlighted. The acoustic radiation measurements are made by a hydrophone located at a few meter distance of the tube. Results are presented as time signals and spectra and are compared to results of analytical and numerical calculations. Relationships between the resonances of the tube and the acoustic radiation in water are then interpreted.