OHS Code Explanation Guide

Published Date: July 01, 2009
Bookmark this page

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 equal-energy 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 time-weighted 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