California Code of Regulations › Title 8 - Industrial Relations › Division 1 - Department of Industrial Relations › Chapter 4 - Division of Industrial Safety › Subchapter 7 - General Industry Safety Orders › Group 15 - Occupational Noise and Ergonomics › Article 105 - Control of Noise Exposure › Appendix A - Noise Exposure Computation

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
I. Computation of Employee Noise Exposure
(a) Noise dose is computed using Table A-1 as follows:
						  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 A-1 or by the formula shown as a
						  footnote to that table.
(b) 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 A-1.
(c) 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.
(d) A table relating dose and TWA is given in Section
						  II.
Table A-1
A-weighted sound level, L
								  (decibel)
Reference Duration T
								  (hour)
A-weighted sound level, L
								  (decibel)
Reference Duration T
								  (hour)
80..........................
32
106..........................
0.87
81..........................
27.9
107..........................
0.76
82..........................
24.3
108..........................
0.66
83..........................
21.1
109..........................
0.57
84..........................
18.4
110..........................
0.5
85..........................
16
111..........................
0.44
86..........................
13.9
112..........................
0.38
87..........................
12.1
113..........................
0.33
88..........................
10.6
114..........................
0.29
89..........................
9.2
115..........................
0.25
90..........................
8
116..........................
0.22
91..........................
7.0
117..........................
0.19
92..........................
6.1
118..........................
0.16
93..........................
5.3
119..........................
0.14
94..........................
4.6
120..........................
0.125
95..........................
4
121..........................
0.11
96..........................
3.5
122..........................
0.095
97..........................
3.0
123..........................
0.082
98..........................
2.6
124..........................
0.072
99..........................
2.3
125..........................
0.063
100..........................
2
126..........................
0.054
101..........................
1.7
127..........................
0.047
102..........................
1.5
128..........................
0.041
103..........................
1.3
129..........................
0.036
104..........................
1.1
130..........................
0.031
105..........................
1
In the above table, the reference duration, T, is
						  computed by
T = 8 / 2 %g(L-90)/5%g
where L is the measured A-weighted sound level.
II. Conversion Between "Dose" and "8-Hour Time-Weighted
						  Average" Sound Level.
Noise exposure is usually measured with an
						  audiodosimeter which gives a readout in terms of "dose." 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, use Table A-2. This table applies to dosimeters that are set to calculate
						  dose or percent exposure according to the relationships in Table A-1. 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-2, 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-2
Conversion from "Percent Noise
								  Exposure" or "Dose" to "8-Hour Time-Weighted Average Sound Level" (TWA)
Dose or Percent Noise
								  Exposure
TWA
Dose
								  or Percent Noise Exposure
TWA
Dose
								  or Percent Noise Exposure
TWA
10..........................
73.4
116..........................
.......................... 91.1
510..........................
..........................
								  101.8
15..........................
76.3
117..........................
.......................... 91.1
520..........................
..........................
								  101.9
20..........................
78.4
118..........................
.......................... 91.2
530..........................
..........................
								  102.0
25..........................
80.0
119..........................
.......................... 91.3
540..........................
..........................
								  102.2
30..........................
81.3
120..........................
.......................... 91.3
550..........................
..........................
								  102.3
35..........................
82.4
125..........................
.......................... 91.6
560..........................
..........................
								  102.4
40..........................
83.4
130..........................
.......................... 91.9
570..........................
..........................
								  102.6
45..........................
84.2
135..........................
.......................... 92.2
580..........................
..........................
								  102.7
50..........................
85.0
140..........................
.......................... 92.4
590..........................
..........................
								  102.8
55..........................
85.7
145..........................
.......................... 92.7
600..........................
..........................
								  102.9
60..........................
86.3
150..........................
..........................
								  92.9
610..........................
.......................... 103.0
65..........................
86.9
155..........................
.......................... 93.2
620..........................
..........................
								  103.2
70..........................
87.4
160..........................
.......................... 93.4
630..........................
..........................
								  103.3
75..........................
87.9
165..........................
.......................... 93.6
640..........................
..........................
								  103.4
80..........................
88.4
170..........................
.......................... 93.8
650..........................
..........................
								  103.5
81..........................
88.5
175..........................
.......................... 94.0
660..........................
..........................
								  103.6
82..........................
88.6
180..........................
.......................... 94.2
670..........................
..........................
								  103.7
83..........................
88.7
185..........................
.......................... 94.4
680..........................
..........................
								  103.8
84..........................
88.7
190..........................
.......................... 94.6
690..........................
..........................
								  103.9
85..........................
88.8
195..........................
.......................... 94.8
700..........................
..........................
								  104.0
86..........................
88.9
200..........................
.......................... 95.0
710..........................
..........................
								  104.1
87..........................
89.9
210..........................
.......................... 95.4
720..........................
..........................
								  104.2
88..........................
89.1
220..........................
.......................... 95.7
730..........................
..........................
								  104.3
89..........................
89.2
230
								  ..........................
.......................... 96.0
740..........................
..........................
								  104.4
90..........................
89.2
240..........................
.......................... 96.3
750..........................
..........................
								  104.5
91..........................
89.3
250..........................
.......................... 96.6
760..........................
..........................
								  104.6
92..........................
89.4
260..........................
.......................... 96.9
770..........................
..........................
								  104.7
93..........................
89.5
270..........................
.......................... 97.2
780..........................
..........................
								  104.8
94..........................
89.6
280..........................
.......................... 97.4
790..........................
..........................
								  104.9
95..........................
89.6
290..........................
.......................... 97.7
800..........................
..........................
								  105.0
96..........................
89.7
300..........................
.......................... 97.9
810..........................
..........................
								  105.1
97..........................
89.8
310..........................
.......................... 98.2
820..........................
..........................
								  105.2
98..........................
89.9
320..........................
.......................... 98.4
830..........................
..........................
								  105.3
99..........................
89.9
330..........................
..........................
								  98.6
840..........................
.......................... 105.4
100..........................
90.0
340..........................
.......................... 98.8
850..........................
..........................
								  105.4
101..........................
90.1
350..........................
.......................... 99.0
860..........................
..........................
								  105.5
102..........................
90.1
360..........................
.......................... 99.2
870..........................
..........................
								  105.6
103..........................
90.2
370..........................
.......................... 99.4
880..........................
..........................
								  105.7
104..........................
90.3
380..........................
.......................... 99.6
890..........................
..........................
								  105.8
105..........................
90.4
390..........................
..........................
								  99.8
900..........................
.......................... 105.8
106..........................
90.4
400..........................
.......................... 100.0
910..........................
..........................
								  105.9
107..........................
90.5
410..........................
.......................... 100.2
920..........................
..........................
								  106.0
108..........................
90.6
420..........................
.......................... 100.4
930..........................
..........................
								  106.1
109..........................
90.6
430..........................
.......................... 100.5
940..........................
..........................
								  106.2
110..........................
90.7
440..........................
.......................... 100.7
950..........................
..........................
								  106.2
111..........................
90.8
450..........................
.......................... 100.8
960..........................
..........................
								  106.3
112..........................
90.8
460..........................
.......................... 101.0
970..........................
..........................
								  106.4
113..........................
90.9
470..........................
.......................... 101.2
980..........................
..........................
								  106.5
114..........................
90.9
480..........................
.......................... 101.3
990..........................
..........................
								  106.5
115..........................
91.1
490..........................
.......................... 101.5
999..........................
..........................
								  106.6
500..........................
..........................
								  101.6
1. Edit
						  correorialction of Table A-1 filed 3-22-84; effective thirtieth day thereafter
						  (Register 84, No. 12).
2. Amendment of Table A-1 filed 8-28-84;
						  effective thirtieth day thereafter (Register 84, No. 35).
3. Change
						  without regulatory effect amending Table A-2 filed 4-14-2009 pursuant to
						  section 100, title 1, California Code of
						  Regulations (Register 2009, No. 16).
Note: Authority cited and Reference: Section
							 142.3, Labor
							 Code.