the nature of sound - travellin...the nature of sound author sarah.irwin created date 7/22/2011...
TRANSCRIPT
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The Nature of Sound
Section 3:
Interactions of Sound Waves
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Essential Questions
How are echos made?
How can an echo help locate an object?
What is constructive interference?
What is destructive interference?
What is resonance?
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Vocabulary
Echo – the bouncing back of a sound wave after striking a barrier
Echolocation – using reflected sound waves to find objects
Interference – combination of two or more waves into one wave• Can be constructive or destructive
Sonic boom – loud boom caused by an object traveling faster than the speed of sound
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Vocabulary, continued
Standing wave – pattern of vibrations that look like a wave that is standing still
Resonance – when a vibrating object causes a second object to vibrate
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Reflection of Sound Waves
Reflection – sound waves bouncing back after striking an object
• Also known as an echo
Echolocation – using echoes to find an object
• Used by some animals: dolphins, bats, some whales, some birds
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Reflection of Sound Waves 2
Sonar (sound navigation and ranging) –electronic echolocation
• Sonar uses ultrasonic waves to find objects or create maps
Ultrasonography – using echoes to “see” inside a patient’s body
• Safer than x-rays
• Ex: commonly used to “look at” developing fetuses
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Interference of Sound Waves
Interference – when two or more sound waves overlap
• Constructive interference – when waves overlap, the amplitude is increased so the sound becomes louder (Think: constructive = build)
• Destructive interference – waves begin to cancel each other out, decreasing the amplitude so the sound becomes softer (think: destructive = tear down)
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Interference of Sound Waves 2 Supersonic speeds – faster than the
speed of sound
• The constructive interference creates a shock wave
Sonic boom – sound heard when a shock wave has occurred
• Can damage hearing and objects
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Interference of Sound Waves 3
Standing wave – a wave that looks like it is standing still
• Maximum amplitude = constructive interference
• Seems to be still = destructive interference
Fundamental frequency – the one standing wave that you can see
Resonant frequency – frequency where standing waves can be seen
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Resonance
Resonance – when a vibrating object causes a second object to vibrate
Used in musical instruments