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MSD Manual

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Measurement of Loudness

Measurement of Loudness

Loudness is measured on a logarithmic scale. This means that an increase of 10 decibels (dB) represents a 10-fold increase in sound intensity and a doubling of the perceived loudness. Thus, 20 dB is 100 times the intensity of 0 dB and seems 4 times as loud; 30 dB is 1,000 times the intensity of 0 dB and seems 8 times as loud.

Decibels

Example

0

Faintest sound heard by human ear

30

Whisper, quiet library

60

Normal conversation, sewing machine, or typewriter

90

Lawnmower, shop tools, or truck traffic (90 dB for 8 hours per day is the maximum exposure without protection*)

100

Chainsaw, pneumatic drill, or snowmobile (2 hours per day is the maximum exposure without protection)

115

Sandblasting, loud rock concert, or automobile horn (15 minutes per day is the maximum exposure without protection)

140

Gun muzzle blast or jet engine (noise causes pain, and even brief exposure injures unprotected ears, and injury may occur even with hearing protectors)

180

Rocket launching pad

*This level is the mandatory federal standard, but protection is recommended for anything more than very brief exposure to sound levels above 85 dB.