6.3.6

Uses of Sound Waves: Ultrasound Waves

Test yourself

Ultrasound Waves

When ultrasound waves meet a boundary between two different materials, some are reflected. We can work out how far away a boundary is based on how long it takes for reflections to reach a detector. We can use ultrasound waves for both medical and industrial imaging.

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Medicine

  • Doctors use ultrasound to perform scans of a developing foetus.
  • Ultrasound waves can pass through the body.
  • Whenever they reach a boundary between two different materials, some will be reflected. We can detect the reflected waves.
  • A computer processes the timing and distribution of these waves. The computer uses these to produce a video image of the foetus.
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Industry

  • We can use ultrasound to find flaws in objects or materials (e.g. pipes or wood).
  • When ultrasound waves enter a material, they will normally be reflected by the far side of the material.
  • If there is a flaw (e.g. a crack), the waves will be reflected sooner. This tells us that there is a problem.
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Water depth

  • We can use echo sounding to detect objects in deep water and also to measure water depth.
  • We send an ultrasound pulse into the water. When this pulse hits any surface, it is reflected back.
  • We can work out the distance travelled by the sound wave by recording the time between us sending the pulse and detecting the reflection.
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Training dogs

  • 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. This is why humans cannot hear them.

Jump to other topics

1Energy

2Electricity

3Particle Model of Matter

4Atoms & Radiation

5Forces

5.1Basics of Motion

5.2Forces

5.3Effects of Forces

5.4Pressure

6Waves

7Magnetism

8Astrophysics

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