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Home > Physics > Health physics > Using sound

Physics

Using sound

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This revision bite gives you details of what you are expected to know about using sound for your General and Credit Level examination. The following topics are covered: the stethoscope, ultrasonic scanning and noise pollution.

You can revise each of these topics in turn or go to the ones that you think need most of your attention. You may wish to print a hard copy for your reference.

Sound and noise

Sound

  • Sounds are carried by longitudinal waves where the particles of the medium vibrate in the same direction as the energy of the sound is carried. Have a look at the Communcation using waves revision bite for more information on longitudinal waves.
  • Humans can hear sounds in the range 20 hertz to 20,000 hertz. This is often referred to as the range of hearing. Not everyone can hear over all of this range- the numbers are only approximate. In particular the high frequency limit reduces with age.
  • The loudness of a sound is a measure of the amplitude of the wave. The greater the amplitude, the louder the sound.
  • The pitch of a sound is a measure of the frequency of the wave. The higher the frequency, the higher the pitch.

 

Video: Frequency and amplitude

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Video: Frequency and pitch

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Noise

We are virtually always subjected to sounds. Unwanted background sounds are sometimes called noise. When the sound level of this noise rises to higher levels, we refer to this as noise pollution.

Sound levels and noise.

  • Sound levels are measured on a scale known as the decibel (dB) scale. The higher the number the greater is the sound level.
  • Too much noise can damage hearing. Exposure to 90 decibel sound levels for a long time can cause permanent hearing loss. Exposure to a brief sound level of 140 decibels will cause pain and can cause permanent damage to hearing.
  • You should be able to give examples of sound levels in the range 0 decibel to 120 decibels, and also give two examples of noise pollution.

Try this:

Question

The table gives the sound levels of some sources of sound. Enter the following sources of sound in the correct places. (You might want to do this exercise on the sheets you have printed out)

  1. Background noise at home.
  2. At a disco - 1 metre from a loudspeaker.
  3. Normal talking.
  4. Whispering

Source of soundSound level in decibels
threshold of sound0
  20
  40
  60
noise pollution level 90
pneumatic drill - 5 metres away100
  120
threshold of pain 140
Answer

Source of soundSound level in decibels
threshold of sound0
whispering20
background noise at home40
normal talking60
noise pollution level 90
pneumatic drill - 5 metres away100
at a disco - 1 m from a loudspeaker120
threshold of pain 140
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Watch

A pair of hands grip a scientific instrument, a tiny man is seen in the background.

Class Clips

Video clip about how sound travels through solids.

Watch the following video clips to learn more about sound waves:

Amplitude and vibration

Frequency and vibration

Sound travelling through air

Sound travels through liquid

Understanding sound

Sound waves

Play

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Tombstone Timeout

Test out your knowledge of physics with Mia Cadaver's physics game - it's serious fun!

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