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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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
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?)
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
Doppler effect – the change in pitch resulting from a moving sound source (like a siren moving past you)
When something moves faster than sound, sound waves pile up and create a shock wave. (sonic boom)
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)