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Dolphins are extremely and almost constantly vocal. They
are capable of two kinds of sounds. A specialized mechanism
in the nasal passages just below the blow-hole enables them
to emit short, pulse-type sounds. These sounds, called clicks,
can be produced in such rapid succession as to sound like
a buzz or even a duck like quack. The clicks are used as a
form of sonar, in which echoes of sounds from surrounding
objects enable the animals to detect obstacles, other dolphins,
fish, and even tiny bits of matter in the water. The military
uses dolphins and this ability to help them find water minds.
This ability is termed ECHOLOCATION. Some Scientists have
speculated that dolphins also use the sounds to deliver an
acoustic shock for stunning of killing small prey.
Echolocation
The term echolocation refers to an ability that odontocetes
(and some other marine mammals and most bats) possess that
enables them essentially to "see" with their ears
by listening for echoes. Odontocetes echolocate by producing
clicking sounds and then receiving and interpreting the resulting
echo. Sound waves travel through water faster than through
air. These sound waves bounce off objects in the water and
return to the dolphin in the form of an echo. High frequency
sounds don't travel far in water. Because of their longer
wavelength and greater energy, low frequency sounds travel
farther.
Echolocation is most effective at close to intermediate range,
about 16 to 656 feet. Dolphins produce a sound in the air
passages in their heads, an oil-filled organ or melon in the
forehead enables dolphins to focus and beam clicks through
the water in front of them. Upon striking an object, the sounds
will reflect, or "echo" back. By interpreting these
echoes, dolphins can distinguish the direction, distance,
speed, size,shape, and even the density of an object. The
closer the dolphin is to a target, the more information he
can acquire.
(MacGillivary Freeman's Dolphins)
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