The influence of marine biological noise on sonar detection

Ocean ambient noise is usually considered as an interfering background for underwater devices. As a key component of ocean ambient noise, marine biological noise also has a serious effect on sonar detection performance. It is found that marine mammal noise has a wide frequency band, with the energy mainly concentrating on low frequency band 10 ~ 500 Hz and medium frequency band 500 Hz ~ 25 kHz, which therefore significantly increases ocean ambient noise. The influence of marine biological noise on sonar detection is simulated with a RAM transmission model. Simulation results reveal that marine mammal noise brings about a drop of the detection range of surface targets from 25 km to 2~10 km. Moreover, the source levels of false killer whales, bottlenose dolphins and sperm whales are all very high, and can propagate over long distances. The frequency band and time duration of these marine mammal noises resemble an active sonar signal, which would result in a higher false alarm rate.