Shipping low frequency noise and its propagation in shallow water

Abstract

One of the most significant factor influencing acoustical climate of the sea is underwater noise generated by moving ships. If the considered sea area has features of the shallow water, namely the wave frequency fulfils relation f < 10c/ h , where c denotes phase speed of sound, and h is depths of the sea, then in certain distance from the wave source specific image of sound pressure distribution in the mean of wave modes appears. The modes constitute wave packet propagating with group speed in the direction parallel to the sea surface. The paper presents results of the experimental investigation concerning the distribution of the sound field created by moving ship in the shallow water, in a small distance from the ship. The main acoustical characteristics, describing features of the field are spectrograms in pseudo-3D system: distance and frequency in geometrical form, and sound intensity in the optical one (color). Results presented in such a way pointed individual features of the sound source known often as acoustical signature of the source (ship).