Daily Noise Dose Level

Daily noise dose when exposed in periods with different noise levels

When the daily noise exposure consists of periods of different noise levels, the daily dose can be calculated as:

D = ( te1 / td1 + te2 / td2 + ... + ten / tdn ) 100%                              (1)

where

D = daily noise exposure (%)

te = exposure time at a specified noise level (min)

td = maximum duration time at specified noise level (min)

According the National Institute for Occupational Safety - NIOSH - the daily dose level - D - should not equal or exceed 100%.

The daily dose can be converted to an 8-hr Time-Weighted Average -TWA by the formula

TWA = 10 log (D / 100) + 85                               (2)

where

TWA = Time Weighted Average noise level (dB)

Daily noise dose as an 8-hr TWA for different daily noise doses:

Daily Noise Dose
(%)
8-hr TWA
(dB(A))
20 78.0
30 79.8
40 81.0
50 82.0
60 82.8
70 83.5
80 84.0
90 84.5
100 85.0
200 88.0
400 91.0
600 92.8
800 94.0
1,000 95.0
1,500 96.8
2,000 98.0
4,000 101.0
6,000 102.8
8,000 104.0
10,000 105.0
20,000 108.0
40,000 111.0
60,000 112.8
80,000 114.0
100,000 115.0
150,000 116.8
200,000 118.0
400,000 121.0
600,000 122.8
800,000 124.0
1,000,000 125.0
2,000,000 128.0
4,000,000 131.0
6,000,000 132.8
8,000,000 134.0
10,000,000 135.0
20,000,000

138.0

Noise level - maximum daily exposure

Example - Daily Noise Dose Level

During a working day a person is exposed to 100 dB in 5 minutes and 94 dB in 30 minutes.

The maximum noise exposure time for 100 dB is 15 minutes and for 94 dB 60 minutes

The daily dose can be calculated as

D = ((5 min) / (15 min) + (30 min) / (60 min)) 100%

   = 83 %

The Time-Weighted Average -TWA can be calculated as

TWA = 10 log (83 / 100) + 85

        =  84 dB 

Related Topics

  • Acoustics - Room acoustics and acoustic properties - decibel A, B and C - Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity and sound attenuation

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