• Part Number:
1910
• Part Number Title:
Occupational Safety and Health Standards
• Subpart:
1910 Subpart G
• Subpart Title:
Occupational Health and Environmental Control
• Standard Number:
• Title:
Noise Exposure Computation
• GPO Source:

Appendix A to § 1910.95 - Noise Exposure Computation

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(C1 / T1 + C2 / T2 + Cn / Tn),

where Cn indicates the total time of exposure at a specific noise level, and Tn 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 log10 (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

A-weighted sound level, L (decibel) Reference duration, T (hour)
80 32
81 27.9
82 24.3
83 21.2
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

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 log10 (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)

Dose or percent noise exposure TWA
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 90.1
116 90.1
117 90.1
118 90.2
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