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=dL-jrqN2iRw

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=r0088hYFuws

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.