Analysis of some special buzz clicks

Toothed whales are known to click regularly to find prey. Once a prey has been detected, the repetition rate of the clicks increases; these sequences are called buzzes. Previous work shows that the buzz clicks spectrum slowly varies from click to click for various species. This spectrum similarity allows buzz clicks association as a sequence using multi-hypothesis tracking (MHT) algorithms. Thus buzz classification follows automatic click tracking. The use of MHT reveals that in some rare cases a variant of this property has been found, whereby sub-sequences of clicks exhibit slowly varying characteristics. In 2010 and 2011, NATO Undersea Research Centre (NURC, now CMRE Centre for Maritime Research and Experimentation) conducted sea-trials with the CPAM (compact Passive Acoustic Monitoring), a volumetric towed array comprised of four or six hydrophones. This configuration allows for a rough estimate of clicking animal localization. Some buzzes with sub-sequences of slowly varying characteristics were reco...