AQA GCSE Physics

Revision Notes

6.1.11 Ultrasound


  • Ultrasound is defined as:

Sound waves with a frequency above the human hearing range of 20 000 Hz

  • The human ear can hear frequencies between 20 Hz and 20 000 Hz

Range of human hearing, IGCSE & GCSE Physics revision notes

The human ear can detect sounds between around 20 and 20 000 Hz in frequency with a peak sensitivity at around 4000 Hz

  • When meeting a boundary between two media ultrasound may be:
    • Partially reflected
    • Partially transmitted
    • Partially absorbed
  • The percentage that is reflected or transmitted depends on the two media at the boundary
    • An air and glass boundary will have different percentages compared to an air and wall boundary
  • The percentage of the wave reflected is greatest when the difference in speed of sound between the media is large
    • For example, when sound in air hits a brick boundary, most of the sound is reflected because waves travel much faster in brick than in air

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