Modeling of Oceanic Ambient Noise at High Frequencies Off Southwest Coast of India

The dominant sources of natural oceanic noise are often due to events occurring at the sea/air interface. Generally field measurements are limited by the response function of the sensors used, such as the spectral bandwidth and sensitivity of the hydrophones, the array beam pattern, and angular resolution. An ambient noise model (based on the ray theory), has been utilised to compute the eigen ray structures for the circular surface point sources. Wind generated surface noise, source levels have been computed empirically. In the present study, an ambient noise model along with transmission loss (TL) model is used to compute the ambient noise at sub-surface depths. Initially for given frequency range (>10KHz) and wind speed, surface ambient noise is computed. This surface ambient noise values are given to TL model to compute ambient noise at sub-surface depths. In the above survey vertical profiles of temperature and salinity along with wind speed were collected from five zonal transects normal to the coast, separated by 30 nautical miles. The environmental conditions are different from transect one to transect three.