8.2.8

Sound Waves

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Sound Waves

Sound waves are longitudinal waves. Pingu is able to hear the music in his headphones because his ear drum vibrates.

Sound Waves and our Ears

Our ears can detect vibrations (compressions and rarefactions) and transfer the information to our brain via our auditory nerve. Our ears are sensitive to (can hear) a range of frequencies between 20Hz and 20,000 Hz.

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Age

  • The range of frequencies that we can hear changes with age.
  • Elderly people tend to become less sensitive to sounds with a higher frequency.
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Ultrasound

  • Ultrasound has a frequency above 20,000Hz. Humans cannot hear sounds with frequencies this high, but other animals can.
  • Dog whistles have frequencies above 20,000Hz, which is why humans cannot hear them.
  • Ultrasound is also used by doctors to perform scans of a developing foetus.

Speed of Sound

Sound needs to travel through a medium. The more rigid the medium is, the higher the speed of the sound wave through the medium. The more compressible the medium is, the slower the speed of the sound wave through the medium.

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Gases

  • Gases are readily compressible (easy to squash), so the speed of sound in a gas is very slow.
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Liquids

  • Liquids are more rigid and less compressible than gases, so the speed of sound in liquids is much higher than in gases.
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Solids

  • Solids are significantly more rigid than liquids and gases and are very hard to compress.
  • Therefore, the speed of sound in solids is much higher than in liquids or gases.

Jump to other topics

1Physical Quantities & Units

2Measurement Techniques

3Kinematics

4Dynamics

5Gravitational Fields

6Deformation of Solids

7Thermal Physics

8Oscillations

9Communication

10Electric Fields

11Current Electricity

12Magnetic Fields

13Modern Physics

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