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Sound

Sound. Sound. Typically the result of vibration of air particles around a source (i.e. speaker) Can travel through solids and liquids as well Longitudinal wave – air particles get compressed and spread apart as vibration propagates. Characteristics of Sound Waves. Pitch = frequency

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Sound

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  1. Sound

  2. Sound • Typically the result of vibration of air particles around a source (i.e. speaker) • Can travel through solids and liquids as well • Longitudinal wave – air particles get compressed and spread apart as vibration propagates

  3. Characteristics of Sound Waves • Pitch = frequency • Human ear most sensitive to sounds between 100 Hz and 20,000 Hz Thunder 20 Hz λ = 17 m Fire Truck Siren 2000 Hz λ = 17 cm Highest pitch heard by humans 20,000 Hz λ = 1.7 cm

  4. Characteristics of Sound Waves • Loudness = amplitude • The more the particles move back and forth the more energy the wave has Decibel Scale (dB) – used to measure loudness of sound times greater than dB level the threshold of hearing Whisper 20 100 Conversation 60 1,000,000 Pain Threshold 120 1,000,000,000,000

  5. Characteristics of Sound Waves • Mechanical Wave – Sound requires a medium • no sound in space • Speed depends on medium • Travels at 331 m/s in air at STP (Reference Tables) • Sound travels faster through solids and liquids than gases • Why did outlaws put their ears to the train tracks or ground to listen for the sheriff? Sound travels faster through solids than gases

  6. Beats • When 2 slightly different frequencies result in waves which go in and out of phase • When in phase - constructive interference - loud • When out of phase - destructive interference - soft http://hyperphysics.phy-astr.gsu.edu/hbase/sound/beat.html

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