Short-finned pilot whale calls and whistles
Whistles are tonal signals showing harmonic spectrographic structures. Calls subjectively appeared tonal to the human ear, however these sounds have different spectrographic appearances. A huge proportion of calls have a complete or partial sideband structure and are presumed to be (fully or partially) pulsed sounds. Whistles as well as calls can rise and fall as well as being levelled or multiply modulated in their contour.
Click ...here... to hear several calls (.mp3 file with 0.4 MB)
The sound example (and spectrographic image) contains several calls in row. Most of them are repetitive and can be heared several times during this sequence. As you can see on the spectrogram, calls sometimes overlap each other because several whales emit their single call at the same time.
Call (and whistle) matching
Own research (...here...) showed that the majority of all recorded vocalizations for short-finned pilot whales southwest off Tenerife, Canary Islands, were calls and whistles. The spectrographic analysis of these calls and whistles showed that most of these vocalizations were heard more than once and up to 36 times during recording sessions (...e.g. here...) whereas just a few were only heard once.