Ch. 18 - Waves & Sound
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Transcript of Ch. 18 - Waves & Sound
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Ch. 18 - Waves & Sound
II. The Nature of Sound Speed of Sound Human hearing Doppler effect Seeing with sound
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A. Speed of Sound
344 m/s in air at 20°CDepends on:
Type of medium• travels better through liquids and solids• can’t travel through a vacuum
Temperature of medium• travels faster at higher temps
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B. Human Hearing
sound wave
vibrates ear drum
amplified by bones
converted to nerve impulses in cochlea
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B. Human Hearing
Pitchhighness or
lowness of a sound
depends on frequency of sound wave
human range: 20 - 20,000 Hz
ultrasonic waves
subsonic waves
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B. Human Hearing
Intensityvolume of sounddepends on energy (amplitude) of sound
wavemeasured in decibels (dB)
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B. Human Hearing
7080
100110
120
40
1810
0
DECIBEL SCALE
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C. Doppler Effect
Doppler Effectchange in wave frequency
caused by a moving wave source
moving toward you - pitch sounds higher
moving away from you - pitch sounds lower
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C. Doppler Effect
Stationary source Moving source Supersonic source
same frequency in all directions
waves combine to produce a shock wave
called a sonic boom
higher frequency
lower frequency
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D. Seeing with Sound
Ultrasonic waves - above 20,000 Hz
Medical Imaging SONAR“Sound Navigation Ranging”