Occupational Safety and Health Standards: Occupational Health and Environment Control, Noise exposure computation

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This Appendix is Mandatory

I. Computation of Employee Noise Exposure

(1) Noise dose is computed using Table G-16a as follows:

(i) When the sound level, L, is constant over the entire work shift, the noise dose, D, in percent, is given by: D=100 C/T where C is the total length of the work day, in hours, and T is the reference duration corresponding to the measured sound level, L, as given in Table G-16a or by the formula shown as a footnote to that table.

(ii) When the workshift noise exposure is composed of two or more periods of noise at different levels, the total noise dose over the work day is given by:

D = 100 (C(1)/T(1) + C(2)/T(2) + ... + C(n)/T(n)),

where C(n) indicates the total time of exposure at a specific noise level, and T(n) indicates the reference duration for that level as given by Table G-16a.

(2) The eight-hour time-weighted average sound level (TWA), in decibels, may be computed from the dose, in percent, by means of the formula: TWA = 16.61 log(10) (D/100) + 90. For an eight-hour workshift with the noise level constant over the entire shift, the TWA is equal to the measured sound level.

(3) A table relating dose and TWA is given in Section II.

TABLE G-16A

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Reference

A-weighted sound level, L (decibel) duration,

T (hour)

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80................................... 32

81................................... 27.9

82................................... 24.3

83................................... 21.1

84................................... 18.4

85................................... 16

86................................... 13.9

87................................... 12.1

88................................... 10.6

89................................... 9.2

90................................... 8

91................................... 7.0

92................................... 6.1

93................................... 5.3

94................................... 4.6

95................................... 4

96................................... 3.5

97................................... 3.0

98................................... 2.6

99................................... 2.3

100.................................. 2

101.................................. 1.7

102.................................. 1.5

103.................................. 1.3

104.................................. 1.1

105.................................. 1

106.................................. 0.87

107.................................. 0.76

108.................................. 0.66

109.................................. 0.57

110.................................. 0.5

111.................................. 0.44

112.................................. 0.38

113.................................. 0.33

114.................................. 0.29

115.................................. 0.25

116.................................. 0.22

117.................................. 0.19

118.................................. 0.16

119.................................. 0.14

120.................................. 0.125

121.................................. 0.11

122.................................. 0.095

123.................................. 0.082

124.................................. 0.072

125.................................. 0.063

126.................................. 0.054

127.................................. 0.047

128.................................. 0.041

129.................................. 0.036

130.................................. 0.031

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In the above table the reference duration, T, is computed by

where L is the measured A-weighted sound level.

II. Conversion Between "Dose" and "8-Hour Time-Weighted Average"

Sound Level

Compliance with paragraphs (c)-(r) of this regulation is determined by the amount of exposure to noise in the workplace. The amount of such exposure is usually measured with an audiodosimeter which gives a readout in terms of "dose." In order to better understand the requirements of the amendment, dosimeter readings can be converted to an "8-hour time-weighted average sound level." (TWA).

In order to convert the reading of a dosimeter into TWA, see Table A-1, below. This table applies to dosimeters that are set by the manufacturer to calculate dose or percent exposure according to the relationships in Table G-16a. So, for example, a dose of 91 percent over an eight hour day results in a TWA of 89.3 dB, and, a dose of 50 percent corresponds to a TWA of 85 dB.

If the dose as read on the dosimeter is less than or greater than the values found in Table A-1, the TWA may be calculated by using the formula: TWA = 16.61 log(10) (D/100) + 90 where TWA=8-hour time-weighted average sound level and D = accumulated dose in percent exposure.

TABLE A-1 - CONVERSION FROM "PERCENT NOISE EXPOSURE"

OR "DOSE" TO "8-HOUR TIME-WEIGHTED

AVERAGE SOUND LEVEL" (TWA)

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Dose or percent noise exposure TWA

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10 ............................. 73.4

15 ............................. 76.3

20 ............................. 78.4

25 ............................. 80.0

30 ............................. 81.3

35 ............................. 82.4

40 ............................. 83.4

45 ............................. 84.2

50 ............................. 85.0

55 ............................. 85.7

60 ............................. 86.3

65 ............................. 86.9

70 ............................. 87.4

75 ............................. 87.9

80 ............................. 88.4

81 ............................. 88.5

82 ............................. 88.6

83 ............................. 88.7

84 ............................. 88.7

85 ............................. 88.8

86 ............................. 88.9

87 ............................. 89.0

88 ............................. 89.1

89 ............................. 89.2

90 ............................. 89.2

91 ............................. 89.3

92 ............................. 89.4

93 ............................. 89.5

94 ............................. 89.6

95 ............................. 89.6

96 ............................. 89.7

97 ............................. 89.8

98 ............................. 89.9

99 ............................. 89.9

100 ............................ 90.0

101 ............................ 90.1

102 ............................ 90.1

103 ............................ 90.2

104 ............................ 90.3

105 ............................ 90.4

106 ............................ 90.4

107 ............................ 90.5

108 ............................ 90.6

109 ............................ 90.6

110 ............................ 90.7

111 ............................ 90.8

112 ............................ 90.8

113 ............................ 90.9

114 ............................ 90.9

115 ............................ 91.1

116 ............................ 91.1

117 ............................ 91.1

118 ............................ 91.2

119 ............................ 91.3

120 ............................ 91.3

125 ............................ 91.6

130 ............................ 91.9

135 ............................ 92.2

140 ............................ 92.4

145 ............................ 92.7

150 ............................ 92.9

155 ............................ 93.2

160 ............................ 93.4

165 ............................ 93.6

170 ............................ 93.8

175 ............................ 94.0

180 ............................ 94.2

185 ............................ 94.4

190 ............................ 94.6

195 ............................ 94.8

200 ............................ 95.0

210 ............................ 95.4

220 ............................ 95.7

230 ............................ 96.0

240 ............................ 96.3

250 ............................ 96.6

260 ............................ 96.9

270 ............................ 97.2

280 ............................ 97.4

290 ............................ 97.7

300 ............................ 97.9

310 ............................ 98.2

320 ............................ 98.4

330 ............................ 98.6

340 ............................ 98.8

350 ............................ 99.0

360 ............................ 99.2

370 ............................ 99.4

380 ............................ 99.6

390 ............................ 99.8

400 ............................ 100.0

410 ............................ 100.2

420 ............................ 100.4

430 ............................ 100.5

440 ............................ 100.7

450 ............................ 100.8

460 ............................ 101.0

470 ............................ 101.2

480 ............................ 101.3

490 ............................ 101.5

500 ............................ 101.6

510 ............................ 101.8

520 ............................ 101.9

530 ............................ 102.0

540 ............................ 102.2

550 ............................ 102.3

560 ............................ 102.4

570 ............................ 102.6

580 ............................ 102.7

590 ............................ 102.8

600 ............................ 102.9

610 ............................ 103.0

620 ............................ 103.2

630 ............................ 103.3

640 ............................ 103.4

650 ............................ 103.5

660 ............................ 103.6

670 ............................ 103.7

680 ............................ 103.8

690 ............................ 103.9

700 ............................ 104.0

710 ............................ 104.1

720 ............................ 104.2

730 ............................ 104.3

740 ............................ 104.4

750 ............................ 104.5

760 ............................ 104.6

770 ............................ 104.7

780 ............................ 104.8

790 ............................ 104.9

800 ............................ 105.0

810 ............................ 105.1

820 ............................ 105.2

830 ............................ 105.3

840 ............................ 105.4

850 ............................ 105.4

860 ............................ 105.5

870 ............................ 105.6

880 ............................ 105.7

890 ............................ 105.8

900 ............................ 105.8

910 ............................ 105.9

920 ............................ 106.0

930 ............................ 106.1

940 ............................ 106.2

950 ............................ 106.2

960 ............................ 106.3

970 ............................ 106.4

980 ............................ 106.5

990 ............................ 106.5

999 ............................ 106.6

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