Chapter 16.5: Using Sound

Pg. 564-567

Echolocation

• Echolocation is the use of reflected sound waves to determine distances or to locate objects

• Animals, including bats and dolphins, use echolocation to navigate and find food

Echolocation: Bats• Bats use ultrasound waves

with frequencies up to 100,000 Hz to move around and hunt

• As bats fly they send out short pulses of ultrasound waves– About 200 pulses per second!– Ultrasound waves reflect off

objects and return the bat’s ears– The time it takes for the sound

to return to the bat lets the bat know how far away the object is

Echolocation: Dolphins, Porpoises, and Whales

• Some animals must hunt in darkness

• Dolphins send out ultrasound waves with frequencies as high as 150,000 Hz– The sound waves travel

through the water and bounce off fish or prey

– Dolphins sense the reflection through their jawbones

Ultrasound Technologies

• Ultrasound technologies such as sonar and ultrasound imaging are used to observe things that cannot be seen directly

Sonar• Sonar is a system that uses reflected sound

waves to detect and locate objects underwater– SOund– Navigation – finding your way around on the

ocean/air– And – Ranging – finding the distance between objects

• Sonar is used to determine the depth of water, map the ocean floor, locate sunken ships, find schools of fish

How Sonar Works:

• A sonar device sends a burst of ultrasound waves that travel through water

• When the sound waves strike an object or the ocean floor they reflect

• The sonar device detects the reflected waves– The farther a sound waves travels without

bouncing off and object, the longer it takes for it return to the sonar device

How Sonar Works: • A computer in the sonar device measures the

time it takes for the sound waves to go out and return – It multiples this time by the speed of sound in

water, which = the total distance the sound waves traveled

– This total distance is then divided by two because the sound waves traveled out and back

Ultrasound Imaging

• Doctors use ultrasound imaging to look inside the human body

• Ultrasound imaging devices send ultrasound waves into the body and detect the reflected sound waves– Different parts of the body reflect sound differently

• The device uses the reflected ultrasound waves to create a picture called a sonogram– Sonograms can be used to diagnose and treat

many medical conditions

Ultrasound Imaging• Ultrasound imaging is used to

examine developing babies before they are born– A small probe is placed on a pregnant

woman’s abdomen– The probe sends out very high

frequency ultrasound waves (4 million Hz)

– The reflected sound waves are analyzed by the device and a sonogram is produced • The sonogram can show the position of

the baby and how many babies are going to be born

http://www.youtube.com/watch?v=YBv79LKfMt4