Echolocation clicks of two free-ranging, oceanic delphinids with different
food preferences: false killer whales Pseudorca crassidens and Risso's
dolphins Grampus griseus
P. T. Madsen, I. Kerr, and R. Payne
J Exp Biol 2004;207 1811-1823
http://jeb.biologists.org/cgi/content/abstract/207/11/1811?etoc