Evaluation of complex broadband biomimetic waveforms for active sonar

Abstract

There is an expanding requirement to reduce the impact of man-made sound, including active sonar transmissions, on marine mammals in the defence, offshore, and other sectors. One way this might be achieved in sonar applications is to use signals derived from natural sounds such as the vocalizations of the animals themselves. It might be expected that such sounds would appear more familiar, thus reducing possible abnormal behavioral impacts. This paper reviews the use of such waveforms and presents the results from a trial designed to compare the detection capabilities of a variety of broadband signals, both conventional and ‘novel’, with a medium frequency active sonar. Two biomimetic signals were tested, one based on sperm whale echolocation clicks and the other on pilot whale whistles. Preliminary analysis suggests the detection performance of these signals using conventional matched filters is comparable with linear FM chirps with a similar bandwidth, but may be improved with detection techniques commonly used for marine mammal vocalizations, such as spectrogram correlation. The paper will conclude with an assessment of the potential impacts of such signals on marine life.