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Sound
3. What is sound
From your physics or science class you probably remember that sound is actually the subtle movement of air (vibration) causing your eardrum to move in sympathy.
Your brain senses this eardrum movement as 'sound'.
Sound is measured in 'cycles per second' or 'Hertz'. This is the frequency of sound. The higher the frequency, the higher-pitched it sounds.
If you have headphones, listen to the two pure tones in the table below. One is low frequency and the other is high frequency.
| Click on these to listen | Comment |
|---|---|
| Low frequency (about 200Hz).mp3 | This is a low frequency pure tone |
| High frequency (about 10KHz).mp3 | This is a high frequency tone |
Human ears (young ones at least!) can hear from 20 Hz to 20,000 Hz. But, as you get older, you lose the ability to hear tones on the higher end of the scale.
As well as the frequency of vibration, there is also the loudness of the sound. Sound is a wave - the loudness is in effect, the height of the wave. This is called the 'amplitude' of the sound:
