Click on the link above the chart to hear the dolphin whistles.
Every dolphin has it's own unique 'signature whistle'. Listening to these whistles is one way to identify specific dolphins and track their whereabouts.
Here's an extract from an article that appeared recently in 'Ear on the SEA' E-zine (which you can get for Free). It describes the work done at the Dolphin Study Group in Singapore:
"Bottlenose dolphins ( Tursiops truncatus ) have elaborate sound
production and receiving systems. In the Tursiops, four major
types of vocalisations have been identified: whistles, clicks,
burst pulsed sounds and chirps."
"Whistles are used in communication. They are continuos,
narrow-band, frequency-modulated pure tones, limited in
frequency to the mid- and upper- range of the sonic spectrum,
generally from 4 to 24 kHz, and of 0.5s in duration. Most of
their energy is below 20 kHz.
"Clicks are directional and used for echolocation. These are
short, broad-band pulses ranging from .2 to 150 kHz. Pulse
duration is 50 to 80 ms. The interclick interval ranges from 10ms
to ~160ms. Dolphins are able to click and whistle at the same
"Burst pulsed sounds occur commonly in social and emotional
context and are thought to be used for communication. These are
trains of clicks with repetition rates of up to 5000 clicks per
second. The high repetition rate gives a tonal quality to the
"Chirps are thought to be used in communication. These sounds are
pulsed, frequency-modulated, broad-band sounds. Frequency
modulation occurs in different frequency bands"
All of the communications related sounds are well within the
human hearing range. Even the echolocation clicks can have
audible components within the nominal 20kHz upper limit of human
hearing - some go down to 0.2 kHz as stated above.
Dolphin whistles were observed with both upward and downward
sweeps. An up-sweep occurs when the whistle starts at a low
frequency and the pitch increases, while in a down-sweep it
starts high then decreases pitch. Sometimes a whistle starts,
sweeps up then abruptly sweeps down. "Of the 20 down-sweep
whistles mentioned, 16 do not have following vocalisation. This
suggests that dolphin vocalisations may be produced in sequences
that end with a down-sweep whistle. A down-sweep whistle may
therefore be a termination signal at the end of a vocal sequence
or a termination signal in a sequence of vocal exchange between
The study was based on a 63 minute tape made at Parc Asterix in
France in 1996. The 'subjects' were 5 adult dolphins and one
calf. The researchers did not see the dolphins nor were they
able to correlate the animals actions with the sounds they
produced. But, it gives us a good base to understand the kind of
vocalisations we will hear in the wild.
This research project is also an excellent example of the quality
of work that can be produced from a 'single encounter' using
readily available tools. DolphinEar and the software included in the package can get you started in your own research. Casual
encounters with dolphins lasting 20-30 minutes are not unusual in
most areas of the world. If you've got your video camera handy
(with the hydrophone plugged into the camera), the visual and
audio record of the event will let you analyze dolphin sounds
and correlate their actions with particular vocalisations. If
don't have time to analyze the tape yourself, there are many
other researchers who would love to have access to it.
~ You can download a copy of the research paper (which includes
many spectrograms and details of their methodology) at:
~ For more information about Dolphin Research have a look at the
excellent website run by Etienne Douze at the University of
Singapore. It can be found at: http://dsg.sbs.nus.edu.sg/
Click on the banner at the top of this page to get a free subscription to 'Ear on the Sea' E-zine.
Article copyright 1999 Arretec. All Rights Reserved. (contact firstname.lastname@example.org for permission to reproduce)