Intensity. A whisper across an empty room is between 0 and 1 db. The intensity of sound is minimal. A jet engine would have the db level of 120 and be painful and damaging to the eardrums.
Here's a scale:
10 dBA: leaves blowing in the wind
20-40 dBA: a regular run-of-the-mill computer
30-60 dBA: a server (like the big professional comany ones. My Dell poweredge server weighs in at about 55-65 dBA depending on temps and load)
75-95 dBA: a car
85 dBA: Here it starts damageing your hearing. Most MP3 players have a software limit at this level, ie. highest setting.
~ 100 dBA: a motorcycle, Harley Davidsons and choppers are louder than this.
110 dBA: a rock concert
120 dBA: a jet airplane taking off (props are louder)
>200 dBA: a nuclear blast from 2 kms away. If you didn't burn to death, your eardrums would vaporize and even kill you because of the sheer sound pressure.
Source: http://forums.techarena.in/off-topic-chat/1217253.htm