Sound level

A sound wave is an expression of a change in air pressure, where the source of sound is the deciding factor for how big the pressure changes are. A split of the audible area cannot be done as a rule.

A small increase in a pressure change by a little volume of sound results in a significant audible difference. In contrast, a small increase in a pressure change by a lot of volume of sound does not result in the same audible impression. The reason for this is that the ear only registers a change in relation to the original strength.

Therefore a scale of strength with intervals which grow proportionately with the
strength is used. This is known as the decibel scale. (dB).

A decibel is a proportional measurement of energy or force and it is organised logarithmically. The choice of a logarithmic scale overcomes several problems and is roughly equivalent to the sound level that is characteristic for the ear. As an example, the doubling of a perceived sound level is the equivalent to a 10dB change.