An introduction to sound

What is sound? 

A sound is a vibration of air, a variation in air pressure, that makes the membrane of the ear vibrate thus becoming "audible".


Sound frequency

Different types of sounds can be defined by measuring the frequency of sound waves per second in the unit Hertz (Hz):

  • Higher sounds have a higher frequency of vibrations per second.
  • Lower sounds have a lower frequency of vibrations per second. 

The human ear can only perceive and "hear" those sound waves if their frequency lies between 20 Hz (20 vibrations per second) and 2000 Hz (20,000 vibrations per second).

Sound loudness

The loudness of sounds can be defined by measuring their intensity in the unit Decibel (dB):

  • Louder sounds have a higher intensity.
  • Quieter sounds have a lower intensity.

It is worth noting that Decibel are expressed on a logarithmic scale, which makes explaining changes in loudness a little complicated. For instance, a reduction of 7dB means that the sound intensity has been divided by 4. An augmentation by a factor of 1000 corresponds to a 30 dB change in level.

What is noise?

A noise is as an unpleasant, disturbing sound. The perception of a sound can vary from one person to another, but louder sounds are generally considered noise, especially when they have higher frequencies.


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