Dezibel

The decibel (unit symbol dB) is a derived quasi-unit for loudness. It is not a true unit, but rather an indication that the value given is the decadic logarithm of a ratio. Generally speaking, a 10 dB increase in sound pressure is perceived by a person as approximately twice as loud.

Generally speaking, the pain threshold of a sound is about 134 dB. In the case of long-term exposure, however, damage to hearing is assumed to occur from as low as 85 dB.