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sound levels

What is a decibel?

The decibel (dB) is the unit used to measure sound levels, but it is also widely used in electronics to compare signal strengths. It is expressed as the base 10 logarithm of the ratio of the powers of two signals.

dB = 10 log (P1/P2)

Sound is a measurement of moving air pressure because that is the way our ears detect and assimilate sound.

On the decibel scale, 0 dB is the lowest level of sound energy that the human ear can detect. Using the above formula, we find that a sound 10 times more powerful than near total silence is 10 dB, 100 times more powerful is 20 dB, and 1,000 times more powerful is 30 dB.

Here are some common sounds and their decibel ratings:

  • Near total silence - 0 dB
  • A whisper - 15 dB
  • Normal conversation - 60 dB
  • A lawnmower - 90 dB
  • A car horn - 110 dB
  • A rock concert or a jet engine - 120 dB
  • A gunshot or firecracker - 140 dB

Hearing loss can be caused by both the power of the sound as well as the length of exposure. Eight hours of 90-dB sound can cause damage to your ears; any exposure to 140-dB sound causes immediate damage. The Occupational Safety and Health Administration sets the standards for allowable workplace exposure to noise.

 

Regulations (Standards - 29 CFR)
Occupational noise exposure - 1910.951910.95(b)(2)
TABLE G-16 - PERMISSIBLE NOISE EXPOSURES

Duration
(hours/day)
Sound Level
(dBA)
8
90
6
92
4
95
3
97
2
100
1.5
102
1
105
.5 or less
110
.25 or less
115

All EXAIR products operate below sound levels where hearing protection is required.

 

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Last modified at 11/24/2008 3:13 PM by emilymortimer@exair.com
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