

OHS Code Explanation Guide 
Published Date: July 01, 2009
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Part 16 Noise 

Section 218 Worker exposure to noise
Table 1 of Schedule 3 of the OHS Code specifies occupational exposure limits for noise and is shown below as Table 16.1. Table 16.2 is an expanded version of Table 1 of Schedule 3, showing exposure durations at each incremental exposure level. Additional entries can be calculated using either of the following formulas:
Table 16.1 presents the occupational exposure limits for noise based on exposure duration. As noise intensity increases, the amount of time an unprotected worker can be safely exposed to that noise decreases. The limits represent conditions under which it is believed that nearly all workers may be repeatedly exposed without adverse effect on their ability to hear and understand normal speech. The values should not be regarded as fine lines between safe and dangerous noise levels.
A 3 dB exchange rate is used to determine when time of exposure needs to be reduced. Exchange rate is the relationship between noise level and exposure duration. The 3 dB exchange rate is also known as the equalenergy rule or hypothesis (equal amounts of sound energy produce equal amounts of hearing damage, regardless of how the sound energy is distributed in time). On an energy basis, the 3 dB exchange rate permits the calculation of a true timeweighted average exposure to noise. Based on the mathematical relationship for sound power level,
every doubling of energy results in an increase in L of 3 dB. The same relationship does not hold true for the 5 dB exchange rate which was previously used. Therefore, for every 3 dB increase in noise level, the exposure time must be halved.
A ceiling limit of 115 dBA is included in the exposure limits – no unprotected worker exposure is permitted above this ceiling. Above this level it is assumed that the unprotected ear is damaged instantly by the noise (animal research suggests that the critical level is between 115 and 120 dBA).
When daily noise exposure consists of different periods of different noise levels, the daily dose should not exceed 100, as calculated by the following equation:
Table 16.1 Occupational exposure limits for noise (appears as Table 1 of Schedule 3 of the OHS Code)
Exposure Level (dBA) 
Duration 
82 
16 hours 
83 
12 hours and 41 minutes 
84 
10 hours and 41 minutes 
85 
8 hours 
88 
4 hours 
91 
2 hours 
94 
1 hour 
97 
30 minutes 
100 
15 minutes 
103 
8 mintues 
106 
4 minutes 
109 
2 minutes 
112 
56 seconds 
115 and greater 
0 
Table 16.2 Expanded version of Table 16.1
Exposure Level (dBA) 
Duration 
82 
16.0 hours 
83 
12.7 hours 
84 
10.1 hours 
85 
8.0 hours 
86 
6.3 hours 
87 
5.0 hours 
88 
4.0 hours 
89 
3.2 hours 
90 
2.5 hours 
91 
2.0 hours 
92 
1.6 hours 
93 
1.3 hours 
94 
1.0 hours 
95 
48 mintues 
96 
38 minutes 
97 
30 minutes 
98 
24 minutes 
99 
19 minutes 
100 
15 minutes 
101 
12 minutes 
102 
9 minutes 
103 
8 mintues 
104 
6 minutes 
105 
5 minutes 
106 
4 minutes 
107 
3 minutes 
108 
2 minutes 
109 
2 minutes 
110 
1 minute 
111 
1 minute 
112 
56 seconds 
113 
45 seconds 
114 
35 seconds 
115 and greater 
0 
