Estimation of vertical coherence of ship Generated noise in the Bay of Bengal region

Vol.8 No.3

Year: 2013

 
Issue: Feb-Apr

Title : Estimation of vertical coherence of ship Generated noise in the Bay of Bengal region 

Author Name : SIVAKUMAR GANGADHARAM, V.Rajanikanth

Synopsis : 

The Bay of Bengal sea area near by Chennai carries considerable amount of shipping. This mostly originates from traffic to and from the other major ports of India. Shipping noise is the most influence of ambient noise in shallow water areas close to shipping narrow ways . Shipping noise is most evident in the 50-300 Hz frequency range. Shallow water region acts as a high pass filter, with the cut-off frequency increasing as the water get shallower. There is an multiple bottom reflection encountered in shallow water region .So the spatial structure of the ambient noise field strongly depends on the geo acoustic properties of the seabed. The vertical directionality and coherence are stable feature of the ambient noise, which are determined by the seabed. These properties are not varied due to the surface source distribution. The ambient noise field in shallow water region is highly complex due to the waveguide nature of the shallow water environment. The automatic ambient noise measurement system deployed in shallow water region of the Bay of Bengal was used to determine the vertical coherence of ship generated noise. In this paper the vertical coherence for different sea state, level of spectrum and effect of ship noise forcing on coherence pattern are presented.