ABSTRACT
This chapter estimates the background noise by applying two-pass split window (TPSW) and then by subtracting it from the total power spectral density. The signal-to-noise ratio is improved, leading to more accurate extraction of tonal components. There are a wide variety of noise sources present in the underwater environment that are different in frequency range and other inherit parameters. Generally, from the sonar signal processing perspective, they can be classified into four different groups. These are ambient noise, radiated noise, self-noise, and reverberation noise. Ambient noise, unlike other sources, does not come from a particular direction or source. The ambient noise level is the intensity of the ambient noise. The form of the radiated noise in the underwater environment depends on the source of the sound radiator. Submarines, ships, torpedoes, and marine mammals are examples of noise sources. The self-noise mainly gets generated from the vibration of structural parts induced by water flow and rotating as well as reciprocating machinery.
