On the use of the Teager energy operator for the detection of clicks in free-ranging dolphins

Abstract

The detection of individual clicks produced by odontocetes is useful for many bioacoustic tasks such as the analysis of interclick interval, classification of odontocete species, etc. Automation of this task is required for the large data sets gathered by remote instruments that can collect terabytes of information over short time periods. A method is presented that locates individual clicks using the Teager energy operator, which is a time-domain metric designed to measure fast variations in signal energy. The Teager energy of a high-pass filtered signal is analyzed by a rule-based classifier that determines the location of individual clicks. The click start can be determined with very high accuracy. Click ends are reasonably well characterized, but the ends of clicks are difficult to determine, even by human experts, due to the influence of external factors such as acoustic reflections. The proposed method is compared with existing techniques and is demonstrated on the calls of several species of free-ranging odontocetes resident in the Southern California Bight and the Gulf of Mexico: bottlenose dolphins (Tursiops truncatus), short and long beaked common dolphins (Delphinus delphis, Delphinus capensis), Pacific white-sided dolphins (Lagenorhynchus obliquidens), and Risso’s dolphins (Grampus griseus).