Sound and Noise
Sound is measured in decibels, which is abbreviated as dB.

0 dB is the weakest sound a person can hear.
The threshold of pain is in the range 120 - 130 dB.

An increase of 1 dB can barely be heard.
An increase of 3 dB is clearly noticed.
An increase of 10 dB is perceived as a doubling of the sound strength.

Our perception of the sound strength is very dependent on the tone - light or dark. When we measure the sound strength, an A-filter is used to compensate for this and the result is expressed in dB(A).

Noise is all sound that injures, irritates or disturbs.

Noise exposure is the average sound level at the ear measured over a full workday.

Link:
Stųj - At-vejledning D.6.1