Adaptive compensation of noise in a sonar system

The performance of a sonar system on a ship is strongly influenced or even limited by its own and other ship’s noise. Its own noise can have different sound sources. The engine causes disturbing line spectra, the auxiliary equipment can radiate both harmonic signals and white or colored noise signals. Due to the viscous flow during ship movement, disturbing noise can also arise. Interaction between the hydrodynamic flow and the whole ship structure can excite the ship’s own modes, which results in strong natural oscillations (flow noise-induced resonances). Additionally, other loud ships can disturb the sonar processing, too. An adaptive noise reduction method is presented. It is suited to reduce a ship’s own machinery noise, and, with slight variations, also jamming targets. The output of the adaptive method can be calculated in the time domain as well as in the frequency domain. Working in the time-domain, techniques are available which reduce the numerical expense, but some reasons suggest the calculation in the frequency domain. Calculations based on both simulated data and real data recorded at sea are presented.