The decibel (abbreviated dB) is the unit used to measure how loud a sound is. The decibel scale is a little odd because the human ear is incredibly sensitive. Your ears can hear everything from your fingertip brushing lightly over your skin to a loud jet engine. In terms of power, the sound of the jet engine is about 1,000,000,000,000 times more powerful than the smallest sound that your ears can just barely hear. That's a big difference!
On the decibel scale, the smallest audible sound (near total silence) is 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB. Here are some common sounds and their decibel levels:
50 dB    refrigerator
50 - 75 dB washing machine

50 - 75 dB air conditioner
50 - 80 dB electric shaver
55 - 70 dB dishwasher
60 - 85 dB vacuum cleaner
60 - 95 dB hair dryer
65 - 80 dB alarm clock
75 - 85 dB flush toilet
80 dB ringing telephone
110 dB baby crying
90 - 115 dB subway
120 dB ambulance siren
130 dB jackhammer, power drill
130 dB percussion section at symphony
140 dB airplane taking off
95 - 110 dB motorcycle
110 dB symphony concert
110 dB car horn
110 -120 dB rock concert
112  dB CD player on high
117 dB football game (stadium)
150 dB firecracker
157 dB balloon pop
162 dB fireworks (at 3 feet)
163 dB rifle
166 dB handgun
170 dB shotgun