AQA GCSE Physics

Revision Notes

6.1.9 Sound Waves

Higher Tier Only

Sound Waves in Solids

  • Sound waves are vibrations of air molecules
  • When a sound wave comes into contact with a solid those vibrations can be transferred to the solid
    • For example, sound waves can cause a drinking glass to vibrate
    • If the glass vibrates too much the movement causes the glass to shatter
  • Sound is an example of a longitudinal wave, hence it consists of:
    • Compressions – regions of higher density
    • Rarefactions – regions of lower density

Compressions and rarefactions, IGCSE & GCSE Physics revision notes

Sound is a longitudinal wave consisting of compressions and rarefactions – these are areas where the pressure of the air varies with the wave

  • These compressions and rarefactions cause changes in pressure, which vary in time with the wave
    • Therefore, sound is a type of pressure wave
  • When the waves hit a solid, the variations in pressure cause the surface of the solid to vibrate in sync with the sound wave

pressure-waves, IGCSE & GCSE Physics revision notes

When sound waves hit a solid, the fluctuating pressure causes the solid to vibrate

Higher Tier Only

Sound Waves in the Ear

  • Sound waves can be heard by human beings because sound waves are transferred from the air to the solid components of the ear
  • In the case of the human ear, the sound waves are transferred by two main solid components:
    • The eardrum which is made of tissue and skin
    • Three small bones
  • The sound wave travels down the auditory canal towards the eardrum
    • The pressure variations created by the sound wave exert a varying force on the eardrum causing it to vibrate
    • The vibration pattern of the sound waves creates the same pattern of vibration in the eardrum
  • The eardrum vibration is transferred to the three small bones
  • The vibration of these small bones then transfers the vibrations to the inner ear
    • In the inner ear, nerve cells detect the sound and send a message to the brain giving the sensation of sound

Human Ear, downloadable IGCSE & GCSE Physics revision notes

The human ear is made up of several components which turn sound waves into signals which the brain can interpret

  • The transmission of sound to the human ear only works over a limited range of frequencies
    • This limits the range of sound frequencies a human can hear
  • The range of frequencies a human can hear is 20 Hz to 20 000 Hz

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Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.

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