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Published byBenedict Simpson Modified over 7 years ago
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Chapter 16 - 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)
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Sound travels faster through solids and liquids than through air. Sound can only travel as fast as the air molecules. (about 340 m/sec) Will sound travel faster in hot or cold air? (Why?)
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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
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The wavelength (or frequency) of a sound wave determines the pitch. The higher the frequency the shorter the wavelength (more energy) High frequency Low frequency wavelength
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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
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When something moves faster than sound, sound waves pile up and create a shock wave. (sonic boom) Shock Wave
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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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