http://www2.sfu.ca/sonic-studio/handbook/index.html
Heres something I just learned. The decibel system is not added or subtracted, for example a 60 db sound is 10 times louder than a 50 db sound.
Some decibel ratings:
0 db Threshold of hearing
30 db Whisper
40 db Buzz of mosquito
50 db Normal conversation
70 db Vacuum cleaner
100 db Subway or power mower
120 db Rock concert
130 db Jackhammer or machine gun
150 db Nearby jet plane
I'm working on a report of pollution in the ocean and I'm doing a section on noise pollution. Some underwater oil drilling companies use these air cannons to find oil. Those are over 250 db..