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Ch. 18 - Waves & Sound

Ch. 18 - Waves & Sound. II. The Nature of Sound Speed of Sound Human hearing Doppler effect Seeing with sound. A. Speed of Sound. 344 m/s in air at 20°C Depends on : Type of medium travels better through liquids and solids can’t travel through a vacuum Temperature of medium

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Ch. 18 - Waves & Sound

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  1. Ch. 18 - Waves & Sound II. The Nature of Sound • Speed of Sound • Human hearing • Doppler effect • Seeing with sound

  2. A. Speed of Sound • 344 m/s in air at 20°C • Depends on: • Type of medium • travels better through liquids and solids • can’t travel through a vacuum • Temperature of medium • travels faster at higher temps

  3. B. Human Hearing sound wave vibrates ear drum amplified by bones converted to nerve impulses in cochlea

  4. B. Human Hearing • Pitch • highness or lowness of a sound • depends on frequency of sound wave • human range: 20 - 20,000 Hz ultrasonic waves subsonic waves

  5. B. Human Hearing • Intensity • volume of sound • depends on energy (amplitude) of sound wave • measured in decibels (dB)

  6. B. Human Hearing DECIBEL SCALE 120 110 100 80 70 40 18 10 0

  7. C. Doppler Effect • Doppler Effect • change in wave frequency caused by a moving wave source • moving toward you - pitch sounds higher • moving away from you - pitch sounds lower

  8. lower frequency higher frequency C. Doppler Effect Stationary source Moving source Supersonic source waves combine to produce a shock wave called a sonic boom same frequency in all directions

  9. Medical Imaging SONAR “Sound Navigation Ranging” D. Seeing with Sound • Ultrasonic waves - above 20,000 Hz

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