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What are Sound Waves?Sound is a
mechanical wave that is an oscillation of pressure
transmitted through a solid, liquid, or gas,
composed of frequencies within the range of
hearing and of a level sufficiently strong to be heard, or the sensation
stimulated in organs of hearing by such
vibrations.
characteristics of Sound
Frequency ,or its inverse, the periodWavelength Wave numberAmplitudeIntensitySpeedDirectionSometimes speed and direction are
combined as a velocity vector; wave number and direction are combined as a
wave vector.
Ultrasound (Ultrasonic Waves)Ultrasound is cyclic sound pressure
with a frequency greater than the upper limit of human hearing.
Although this limit varies from person to person, it is approximately 20
kilohertz (20,000 hertz) in healthy, young adults and thus, 20 kHz serves
as a useful lower limit in describing ultrasound. The reflection signature
can reveal details about the inner structure of the medium, a property
also used by animals such as bats for hunting. The most well known
application of ultrasound is its use in sonography to produce pictures of fetuses in the human womb. There
are a vast number of other applications as well.
Applications of Ultrasound Bats (to detect
their preys)To detect an
unborn babies' sexRadars Dog whistlesUltra sonography Treatment of
muscular painDetect cracks in
metals
The bat Ultrasonic Location System
A short pulse of ultrasound is emitted from a transmitter (a Bat) attached to the object to be located, and we measure the
times-of-flight of the pulse to receivers mounted at known points on the ceiling.
The speed of sound in air is known, so we can calculate the distances from the Bat
to each receiver - given three or more such distances, we have enough
information to determine the 3D position of the Bat (and hence that of the object
on which it is mounted) .By finding the relative positions of two or
more Bats attached to an object, we can calculate its orientation. Furthermore, we
can deduce some information about the direction in which a person is facing, even if they carry only a single Bat, by analysis
of the pattern of receivers that detected ultrasonic signals from that transmitter, and the strength of signal they detected .