Ultrasound has been used on shattering
calculi, making out the fetus sex,
researching dolphin's language, training
dogs, and cleaning contact lens. Unconsciously,
ultrasonic products become the daily
commodities in our life. Looking at
the goods shelves, all we have to
do is to stretch out the arms and
get it. However, lots of people are
lost in the vastly technological products.
Actually, ultrasound, a high technological
jewel, is going to renew and light
up our life.
What
is ultrasound?
Sound is transformed like a wave,
with different sizes and densities;
different waves emit high and low
sounds. The human's hearing range
is from 20 to 18000Hz. The higher
the Hz is, the higher the tone we
hear. Like the strings of a violin,
the thinnest one always produces the
highest sound. Ultrasound is undetectable
to humans. In engineering, any rate
over 20000Hz is called ultrasound,
i.e. the threshold above 20000 vibrations
per second.
To our hearing, ultrasound is inaudible,
but to many animals, it is heard clearly.
For example, a bat can respond to
20 thousands to 200 thousands Hz of
ultrasound. A dolphin or whale can
also discriminate between hundreds
of thousands Hz of ultrasound. If
ultrasound means nothing to our sense
of hearing, what can we do with it?
We can take the advantage of its density
and speed in more subtle methods.
First of all, we must know exactly
how ultrasound can benefit us.
The
development of ultrasound
Research
on ultrasound began at the start of
the First World War (1914), when the
Allied forces used it to detect Germany
submarines. Except for military purposes,
it was only used for underwater research
- until 1927, when the United States
began to use ultrasound in bio-chemical
research. In 1928, using ultrasound,
the eastern Germans ran experiments
to attempt curing loss of hearing
and otosclerosis, and by 1939, ultrasonic
therapy was born. Although theultrasonic
development was interrupted by the
Second World War, the UK and other
countries actively refined ultrasonic
therapy for rehabilitative purposes
in postwar years.
