Decibel

A decibel or dB measures power or intensity. Most often, it is used to say how loud a sound is relative to the threshold of hearing. At the moment, the decibel is not an SI unit. dB are units of sound mostly for consensus on hearing protection.

Examples and protection

Some examples of sounds are:

Sound Level	Examples
200-250 dB	Cannon at 12 feet
175-200 dB	Saturn Rocket firing
150 dB	Airplane at takeoff
130 dB	Above this can damage the ear quickly, and pain is felt.
120 dB	Diesel engine, ball mill
100 dB	Lawn mower, factory
90 dB	Band or symphony, above this can damage the ear if heard extensively.
80 dB	Police or fire siren, electric shaver
70 dB	Radio sound level, crowded neighborhood.
50 dB	Can normally awaken a sleeping person.
30-35 dB	Very quiet conversation, private office noise
20 dB	Rustling leaves, whispering
10 dB	Sound-proofed room, the minimum most human ears can hear
0 dB	Hearing threshold.

Hearing protection can also be used to shield from ear damage.

Decibels	Maximum Exposure Time
90	8 hours
92	6 hours
95	4 hours
97	3 hours
100	2 hours
102	90 minutes
105	60 minutes
110	30 minutes
115	10–15 minutes
120	3–5 minutes