Characterization of sperm whale vocalization energy based on echolocation signals

Sperm whales (Physeter macrocephalus) emit a train of impulsive echolocation signals called “clicks” when diving in search of food. These acoustic signals can be divided into “usual clicks” and “creaks”. The frequency spectrum of these broadband transient signals is between about 500 Hz and 24 kHz, but most of the energy lies between 2 and 9 kHz. The usual clicks have an inter-click interval (ICI) of 0.5-2 s, whereas the ICI of creaks is less. These click signals consist of multiple pulses which are related to the structure of the sperm whale head. An analysis of these signals is presented based on real data from the Atlantic Undersea Test and Evaluation Center. The motivation is the design of a click energy based sperm whale detector which exploits the characteristics of these signals.