Download Sonar and Echolocation

Sonar and Echolocation
Hunter Layman
Garrett George
What is Sonar
• A way of locating things underwater by
emitting sound waves at either infrasonic or
ultrasonic levels.
• Sonar stands for Sound Navigation Ranging.
• There are two types, Active and Passive.
• http://www.youtube.com/watch?v=dLjrqN2iRw
Active Sonar
• Active sonar transducers emit a signal or pulse
of sound directly into water. If there is an
object or some kind of obstruction, the sound
reflects off the object and returns as an
“echo.”
• There is a lot that can be learned from this
echo such as the distance of the object and
the shape of it.
Passive Sonar
• Systems that use passive sonar focus on
detecting noise from objects such as
submarines or ships and animals.
• Passive Sonar does not emit any sound itself,
which actually has its advantages.
• Practical for military ships and submarines not
wanting to be found.
• Multiple Passive devices may lead to
triangulation of source of sound.
Physics Behind Sonar
• Property of waves: Reflection
• The longer the distance the lower the
frequency.
• http://www.youtube.com/watch?v=r0088hYF
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Multiple Uses
• Sonar is used for detection of submarines and
mines.
• Depth detection.
• Commercial fishing.
• Overall communication at sea.
• Also animals have the ability to use something
similar to Sonar.
What is Echolocation
• Echolocation is the transmission of sound
waves to locate objects
• Used by whales, dolphins, bats, etc…
How it works
• Animals produce a sound wave and listen for
the echo
• The initial sound is very high-pitched
• Humans usually cannot hear the echolocation
sound
Frequency
• Bat calls range from 10,000Hz to 100,000Hz
• Frequency used depends on what its being
used to detect
– Lower frequencies used for moths and other
insects
– Higher frequencies used for navigation
Intensity
• Echolocation calls range between 60dB-140dB
• Bats use a higher intensity for hunting
Call Duration
• A single call can last from 0.2-100 milliseconds
• Duration of the call decreases as the animal
gets closer to the prey
Fun Fact
• Dolphins have demonstrated a remarkable
ability to detect and identify objects through
echolocation, even objects that are buried
under the ocean floor.
• The Navy has begun to train dolphins to
detect buried items not identifiable by human
sonar.