Unit 2 Lesson 3 Sound Technology
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Unit 2 Lesson 3 Sound Technology
Hello Hello Hello
How are echoes used?
• Echolocation is the use of echoes to find food and
other objects.
• Animals produce ultrasound, which are sound
waves that have frequencies greater than 20,000
Hz, for echolocation. The frequencies of these
ultrasonic waves are too high for humans to hear.
• The time it takes for ultrasound to bounce off an
object and return to the animal tells the animal how
far away the object is.
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Unit 2 Lesson 3 Sound Technology
How are echoes used?
• Though people cannot send out or hear
ultrasound, people can still use echolocation in
various technologies.
• Sonar is a system that uses echoes to determine
the locations of objects or to communicate.
• Sonar is used to map out ocean floors, find fish,
avoid icebergs, and help visually impaired people
navigate on land.
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Unit 2 Lesson 3 Sound Technology
How are echoes used?
• How is sonar used to map the ocean floor?
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 3 Sound Technology
How are echoes used?
• Ultrasound procedures use high-frequency sounds
to produce images of the inside of a person’s
body.
• Ultrasound that has a frequency of 1 million to 10
million hertz can pass into a person’s body.
• Ultrasounds do not harm human cells, like x-rays
do.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 3 Sound Technology
How are echoes used?
• The sound waves reflect when they meet internal
organs.
• The reflected waves create an image of whatever
organ they bounce off of.
• Ultrasounds are used to check how a fetus is
growing in a mother’s body.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 3 Sound Technology
How do telephones transmit sound?
• Sound waves lose energy over time.
• Phones change sound waves into other types of
signals that can be sent over long distances.
• These signals are then changed back into sound
waves that can be heard.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 3 Sound Technology
How do telephones transmit sound?
• All telephones change sound into electrical
signals.
• Cordless phones change the electrical signal into
radio waves that travel through air at the speed of
light.
• The base picks up the radio waves and changes
them back into electrical signals that are sent
through wires.
• A computer sends these signals to the other
phone, where they are changed back into sound
waves.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 3 Sound Technology
Hello, Operator
• People used to have to call telephone operators, who
plugged wires into a switchboard to connect one
phone to another.
• The invention of the rotary dial made it possible for
people to call a number directly, replacing telephone
operators.
• Cell phones use radio waves to send signals to phone
towers. The towers transfer the signals to phone
cables.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 3 Sound Technology
Groovy
How is sound recorded and played
back?
• Sound is recorded to preserve sound information,
such as interviews and music.
• Thomas Edison invented the phonograph, which
could record and play back sound.
• Information in sound was recorded in the grooves
of records. Now it is stored on CDs or in computer
files.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 3 Sound Technology
How is sound recorded and played
back?
• A compact disc, or CD, is made of hard plastic.
• The information in sound waves is stored by
pressing microscopic pits into the plastic.
• Light from a laser reflects off the shiny surface as
the CD rotates.
• The detector changes the pattern into an electrical
signal, which is then changed back into sound
waves.
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Unit 2 Lesson 3 Sound Technology
How is sound recorded and played
back?
• How does a laser read a CD?
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 3 Sound Technology
How is sound recorded and played
back?
• Sound is also recorded as a digital file in a
computer.
• Digital files, such as MP3 files, store large
amounts of information.
• More sound files can be stored in a computer or
an MP3 player than on a CD.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 3 Sound Technology
How is sound recorded and played
back?
• First, the original sound gets changed into an
electrical signal.
• Then, it is stored as a digital file on a hard drive.
The digital file is a series of 1s and 0s.
• Software reads the files and produces electrical
signals that are sent to speakers.
• The speakers change the signal back into sound
waves.
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