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Chapter 11 - Sound

Sound waves are longitudinal waves with rarefaction and compression. As an object’s vibration moves toward air it creates a compression As the object moves away from air it creates a partial vacuum (rarefaction). Chapter 11 - Sound.

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Chapter 11 - Sound

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  1. Sound waves are longitudinal waves with rarefaction and compression. As an object’s vibration moves toward air it creates a compression As the object moves away from air it creates a partial vacuum (rarefaction) Chapter 11 - Sound

  2. Sound travels faster through solids and liquids than through air. Sound can only travel as fast as the air molecules. (about 340 m/sec) Q: Will sound travel faster in hot or cold air? (Why?)

  3. The amplitude of a sound wave (the amount of compression) determines the loudness of the sound. Loudness is measured in decibels (dB). Whisper 20 dB Loud conversation 60-70 dB Loud music 90-100 dB (hearing damage starts) Jackhammer 120 dB (pain starts)

  4. The wavelength (or frequency) of a sound wave determines the pitch. • The higher the frequency the shorter the wavelength (more energy) wavelength High frequency wavelength Low frequency

  5. Doppler effect – the change in pitch resulting from a moving sound source (like a siren moving past you) • The frequency changes as an object moves past you. • Higher pitch – moving towards you • Lower pitch – moving away from you

  6. When something moves faster than sound, sound waves pile up and create a shock wave. (sonic boom) Shock Wave

  7. Sonar – uses the time it takes for a sound wave to bounce back to determine distance. (a depth finder) Echolocation uses sonar to locate object (Dolphins, whales and bats use echolocation)

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