**1. Introduction**

Nature is wonderful to observe, study, or analyze its diversity. It had thrown challenges to man in the past, and still this study is ever exploring. For the past many years, acoustics and oceanographic study have been interrelated. Ocean is a pandemonium of different sounds. Underwater acoustics has become the natural interest to many researchers throughout the world for the simple reason that it is so complex to study and analyze. The sources of sound are breaking waves, marine life, various sources of nature, and rain. Shipping also becomes an important factor for the noise generation along with several other man-made sources like military sonar for the source of sound. These sounds exist throughout the year along with the sounds that are seasonal.

Underwater ambient noise is a constituent of background noise that depends on depth, time, and also w.r.t location. Self noise does not belong to the category of ambient noise [1]. Ambient noise is the residual noise that would exist even after recognizable sources of sound are removed. Ship traffic contributes to the major component of ambient noise, whereas the noise generated by a nearby ship is considered as sound signal and is not a part of ambient noise [2].

For valid measurements of ambient noise, all possible sources of self-noise must be eliminated or at least reduced to an insignificant contribution to the total noise level (NL). Self noise sources, such as cable strumming, splashes of waves against the hydrophone cable, and sometimes even crabs crawling on the hydrophone, must be absent.
