Observation and analysis of sonar signal generation in the bottlenose dolphin (Tursiops truncatus): Evidence for two sonar sources

► Nasal phonic lips are the site of sonar signal generation in bottlenose dolphins. ► Evidence indicates at least two sonar signal generators exist in most odontocetes. ► Anatomy suggests that all extant Odontoceti use the phonic lips and similar mechanism. ► Muscular formation of grooves in the nasal mucosa direct air flow to the phonic lips.