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And what is an echo? When sound waves hit
an object they are bounced back or reflected. This reflected sound
is called an echo. The length of time it takes for an echo to be
heard indicates the distance of the object in question. In the case
of animals that use echolocation for navigation, if an object is
approaching the animal which has emitted the sound then the echo
returned is of a higher frequency. This tells the animal about the
imminent approach of the object and it positions itself suitably.
And similarly, if an object is moving away then the reverse is true.
All this is, however, so instantaneous that the animal emits the
sound, receives the echo, evaluates it and changes direction and or
speed without the slightest pause.
Well what are all these animals moving
around for? Food, undoubtedly. Nature, which has given these animals
a way to chase and capture prey, would also have provided the prey
with something to defend itself adequately. And as is the law of
nature – survival of the fittest – the animal that uses his skills
the best survives.
Moths, which are hunted by bats, have soft
scaled wings that muffle the echo. The muffled echo will not give
the chasing bat a correct estimate of the moth’s position. Some
moths have sensors, which warn them of approaching bats. They can
thus move away from danger. Some moths emit clicking sounds.
Echolocation is needed by animals like bats
that are blind or whales and dolphins that need to navigate in the
dark. So why, one would wonder would birds need to use this? Well
not all birds do, only birds like the oil birds and cave swiftlets
use echolocation. They nest in caves where it is dark, hence mother
nature to the rescue. Shrews emit shrill high-pitched cries too, but
as they do not really need it; therefore their echolocation skills
are not as polished as those of say bats or whales.
Knowing all that he does about this
exquisite system used in nature, would man be far behind in using
the technique? Certainly not. We have been using it for quite
sometime now. First only underwater, for purposes of tracking
submarines, locating icebergs, etc. and later with the advent of
computers ultrasound imaging has been put to various uses. Medical
uses are among the most important of them. Ultra sound waves are
directed into a body and they reflect off the internal organs they
come in contact with. These reflected waves with the use of
computers form detailed images that can be seen on a computer
screen. The advent of this technique has made the diagnosis of many
diseases very accurate. |
