Abstract: This paper describes key features of a Mutual Interference Reduction (MIR) in sea area, especially in shallow water, where some acoustic devices may operate simultaneously. MIR is an essential problem in mono– and multistatic systems. Receivers of sonars or barrier modules, operating in these systems, can receive signals from other acoustic devices by direct track, as echoes from the targets or as reverberations. The mutual sonars interference level depends on many parameters, like: the transmitting signal parameters (modulation, SL, B, T) and bands aliasing, mutual sectors coverage, the distance and mutual localization of transmitting transducers and receiving arrays, as well as type of matched filtration. The degradation of mutual interferences by matched filtration has been determined. Influence of modulation type, B and T parameters on MIR at the matched filtration output have been presented also.