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Physical Science

Ch 17-4 Sound and Hearing

State Benchmark P4.5

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Quick Quiz Questions

  • Which type of wave is sound an example of a
    • transverse, longitudinal, surface

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  • This tool sends sound waves into deep water and measures the time delay of the returning echoes.
    • ultrasound, sonar, doppler

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  • An ambulance siren sounds different as it approaches you than when it moves away from you. What scientific term would you use to explain how this happens?
    • ultrasound, sonar, doppler

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  • When a sound source approaches you, the pitch you hear is ___ than when the source is stationary.
    • higher, lower, the same

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Properties of Sound Waves

  • Sound waves - longitudinal waves that carry sound.
  • Speed – in dry air sound travels at 342 m/s. Speed changes based on the media. Fastest in solids, slower in liquids and slowest in gases.
  • Ex. Sound would travel faster through iron then water or air.

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Properties of Sound Waves

  • Intensity – The rate at which sound travels through a given area – depends on amplitude and distance. Measure in decibels (dB)
  • Loudness – your physical response to the intensity.

Pitch – Frequency of a sound as you perceive it.

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Ultrasound

  • Sound at frequencies higher than people can hear. It is used in a variety of techniques including sonar and imaging.
  • Sonar determines the distance to an object under water. It sends a sound wave into water and measures the amount of time it takes for the echo to return.
  • Imaging uses reflected sound to create an image – in utero baby pictures.

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The Doppler Effect

  • Doppler effect is the change in sound frequency caused by the motion of the sound source, motion of the listener, or both.
  • As the sound approaches the listener hears a higher pitch. As the sound source moves away the observer hears a lower frequency.

Also applies to light

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Hearing and the Ear

  • The outer ear gathers sound and focuses it to the middle ear which receives and amplifies the vibrations.
  • The inner ear has nerve endings to sense vibrations and send signals to the brain.

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Music

  • Most musical instruments vary pitch by changing the frequency of the standing waves.
  • Resonance – the response of a standing wave to another wave of the same frequency.
  • Ex. A piano amplifies sound with a wooden soundboard

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Quick Quiz

  • Which type of wave is sound an example of?
    • longitudinal

​

  • This tool sends sound waves into deep water and measures the time delay of the returning echoes.
    • sonar

​

  • An ambulance siren sounds different as it approaches you than when it moves away from you. What scientific term would you use to explain how this happens?
    • Doppler Effect

​

  • When a sound source approaches you, the pitch you hear is ___ than when the source is stationary.
    • higher

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Review

  • Identify the different properties of sound waves.
  • What tools use sound waves?
  • How does motion affect sound?
  • Explain how humans can hear.
  • How do instruments create and amplify musical sound?