The impact of reverberation on active sonar optimum frequency

For many active sonar problems there exists an optimum frequency for detection. In this paper, the optimum frequency is defined as the frequency which maximizes the signal excess of a monostatic active sonar system in shallow water. The optimum frequency is a function of range and can be calculated using the sonar equation which includes several frequency dependent terms. Active sonar in shallow water may be reverberation limited rather than noise limited, which impacts the optimum frequency. Standard Lambert bottom interface scattering strength models are frequency independent, however more accurate data-derived bottom backscatter strength models are frequency dependent. The bottom scattering strength model choice is important for determining the optimum frequency. Finally, volume reverberation due to biological activity (scattering from fish) has a complicated frequency dependence, which changes the optimum frequency. In addition to calculating the optimum frequencies for these cases, this work also quantifies the performance degradation caused by a suboptimum frequency selection.