About Ultrasound; Animal Sonar; Active Sonar - Thames & Kosmos Robotics Smart Machines Experiment Manual

ABOUT ULTRASOUND

ABOUT ULTRASOUND
Ultrasound is a sound pressure wave that moves through
substances (gases, liquids, and solids) and has a
frequency greater than that which humans can hear.
Frequency is simply the number of waves in a given period
of time. Humans can hear sound waves in the frequency
range of 20 hertz (which means cycles per second) to
20,000 hertz (20 kilohertz).

ANIMAL SONAR

In the natural world, bats, whales, and some birds use
sound waves to detect objects around them. This is
especially useful in the darkness of night or underwater,
where seeing visible light is difficult or impossible.
This type of sensing is called echolocation, or biosonar. It
works like this: The animal emits sound waves that move
outward in all directions around it. When the sound waves
hit an object, they bounce off of it and travel back to the
animal's ears. The sound waves reach each of the animal's
two ears at slightly different times. The animal can
interpret this time difference to perceive the size, direction
of movement, and speed of objects.
Animals use echolocation to hunt prey in the dark of
night. They can also navigate and find their way around
without normal eyesight.

ACTIVE SONAR

Humans have developed a technology to replicate
echolocation, which is called sonar. Sonar is an acronym
for SOund Navigation And Ranging. Sonar is used for
navigation in submarines, ships, and airplanes. A similar
technology using electromagnetic radio waves instead of
sound waves is called radar (RAdio Detection And
Ranging).
With sonar and radar, airplane pilots are able to find their
way and avoid collision with other planes, even in
complete darkness or in thick clouds. Police use radar to
detect speeding cars.
Your ultrasonic sensor also sends out sound waves. You
can't hear them because they are ultrasonic! One "eye" on
the sensor head is a transmitter and the other is a receiver.
The transmitter sends out ultrasonic waves, like a
speaker, and the receiver senses the waves that bounce
back, like a microphone. In this way, the sensor is able to
sense objects in front of it, even in the dark.
8
Low Frequency
20 Hz 20 kHz
Infrasound Acoustic
Sound waves of emi ed call
Sound waves sent out
Sound
transmi er
and receiver
Reflected sound waves
The ultrasonic
sensor has one
transmitter and
one receiver.
High
2 MHz 200 MHz
Ultrasound
Echo sound waves
Bat
Dolphin
Submarine
Object