Sonar Optimal Frequency in the Real Ocean Conditions

Marasev S. V., Mashoshin A. I.

The optimal frequency plays an important role in design and usage of different sonar both passive and active. For simplicity the optimal frequency calculation is usually fulfilled with the use of the formulas not taking in account the peculiarities of the signal and sea noise propagation in the concrete conditions. It can entail the mistakes in the optimal frequency choosing. The work is devoted to the passive and active sonar optimal frequency investigation. Investigations were fulfilled taking in account all the factors influencing on the optimal frequency, including signal propagation anomaly and vertical sea noise anisotropy. The investigation showed that in the real ocean conditions the optimal frequency always lower then simplified calculation gives. And the difference depends on the hydroacoustic conditions in the ocean region. The greatest difference takes place in the conditions of positive ray refraction when the propagation of the acoustic energy occurs by reflection of sea surface. In these conditions the optimal frequency value strongly depends on sea state — the greater sea state the lower optimal frequency. The greatest influence of signal propagation anomaly takes place on the distances from 3 to 30 km: on the smaller distances the conditions have weak influence on the signal propagation; on the larger distances the main influence on optimal frequency has spatial fading.

Download original text