Noise exposure computation

Compute the dose with D = 100 × C / T, where C is the total hours worked and T is the reference duration for the measured A-weighted sound level from Table G-16a. See Appendix A to 1910.95 for the formula and Table G-16a.

• Example: For an 8-hour shift at a constant 92 dB, Table G-16a gives T = 6.1 hours, so D = 100×8/6.1 ≈ 131%.

Add the fractional doses from each exposure period using D = 100 × (C1/T1 + C2/T2 + ... + Cn/Tn), where Cn are the hours at each level and Tn are the reference durations from Table G-16a. See Appendix A to 1910.95 for the rule and table.

• Practical steps:
  • Look up T for each measured level L in Table G-16a.
  • Compute each fraction Cn/Tn, sum them, then multiply by 100 to get percent dose.

Compute T using the Table G-16a lookup or the formula T = 8 / 2^{(L - 90)/5}, which yields the same reference durations used in the table. See Appendix A to 1910.95 for Table G-16a and the reference-duration relationship.

• Example: For L = 95 dB, T = 8 / 2^{(95-90)/5} = 8 / 2^{1} = 4 hours (matches Table G-16a).

Convert dose D (percent) to TWA using the formula TWA = 16.61 × log10(D/100) + 90, or use the values in Table A-1 for common doses. See Appendix A to 1910.95 for the formula and Table A-1.

• Example: For D = 91%, TWA = 16.61×log10(0.91)+90 ≈ 89.3 dB (matches Table A-1).

If the A-weighted sound level is constant over an entire 8-hour shift, the 8-hour TWA equals that measured sound level. See the statement in Appendix A to 1910.95 confirming this.

• This is because a constant level over the full 8 hours produces a dose that corresponds to the same dB value on the 8-hour TWA scale.

If the dosimeter dose isn't in Table A-1, calculate TWA with TWA = 16.61 × log10(D/100) + 90 using the dosimeter's percent dose D. See Appendix A to 1910.95 for this guidance.

• Use this formula for doses smaller than the table's minimum or larger than its maximum for precise results.

Use Table G-16a to find the reference duration T for each A-weighted level L; shorter T means a higher-risk level that consumes dose faster. See Appendix A to 1910.95 for the table and its use in dose calculation.

• Example: L = 90 dB has T = 8 hours (full-shift exposure yields 100% dose), while L = 95 dB has T = 4 hours (8 hours would be 200% dose).
• Use these T values to schedule exposure times, rotate employees, or select hearing protection.

Convert the exposure time to hours (C = 0.25 hrs for 15 minutes), find T for 110 dB from Table G-16a (T = 0.5 hrs), then compute D = 100 × C / T = 100 × 0.25 / 0.5 = 50%. See Appendix A to 1910.95 for the table and formula.

• This single short exposure at 110 dB contributes the same dose as 4 hours at 95 dB (both are 50%).

Yes, if the dosimeter is set to calculate dose according to the relationships in Table G-16a, you can convert the manufacturer-read dose directly to an 8-hour TWA using Table A-1 or the TWA formula. This is explained in Appendix A to 1910.95.

• Verify the dosimeter uses OSHA’s exchange rate and reference (Table G-16a) before relying on its percent-dose readout.

A 100% noise dose means the employee has reached the allowable eight-hour exposure at 90 dB (the reference point used in Table G-16a) for that shift; you can also convert it to an 8-hour TWA of 90 dB. See Appendix A to 1910.95 for the dose concept and conversion table.

• If D > 100%, the employee has been exposed above the standard 8-hour limit and controls or hearing protection should be evaluated.

Look up 50% in Table A-1 and read the corresponding TWA: 50% dose corresponds to a TWA of 85.0 dB. See Appendix A to 1910.95 where Table A-1 lists the dose-to-TWA conversions.

• This illustrates that an 8-hour exposure at 85 dB yields a dose of 50%.

You can still apply the reference-duration formula T = 8 / 2^{(L - 90)/5} to compute T for levels below 80 dB and then compute dose with D = 100 × C / T; Table G-16a is a sampled list, and the formula produces consistent reference durations. See Appendix A to 1910.95 for the relationship used to generate the table.

• For very low levels, T will be greater than 32 hours, so typical workshift doses will be well under 100%.

Treat each exposure period separately: determine Cn (hours) and Tn for each noise level and use D = 100 × Σ(Cn / Tn) to get the total daily dose. This method is in Appendix A to 1910.95.

• Include all on-duty noisy periods in the sum; off-duty quiet periods do not add dose.

Yes — the reference duration T halves for every 5 dB increase above 90 dB, which is equivalent to using the formula T = 8 / 2^{(L - 90)/5} and is consistent with Table G-16a in Appendix A to 1910.95.

• Example: 90 dB → T = 8 hr; 95 dB → T = 4 hr; 100 dB → T = 2 hr.

Use TWA = 16.61 × log10(D/100) + 90 with D = 131, giving TWA ≈ 16.61×log10(1.31)+90 ≈ 91.6 dB. See Appendix A to 1910.95 for the conversion formula.

• This shows that combined exposures producing >100% dose correspond to TWAs above 90 dB.

Yes — Table A-1 applies to dosimeters that are set by the manufacturer to calculate dose according to the relationships in Table G-16a (the exchange-rate and reference durations described in Appendix A to 1910.95).

• If a dosimeter uses a different exchange rate or criterion level, you must adjust calculations or settings to match Table G-16a before using Table A-1.

Compute T for each level from Table G-16a (100 dB → T = 2 hr; 92 dB → T = 6.1 hr), then D = 100×(2/2 + 1/6.1) ≈ 100×(1 + 0.164) = 116.4%. Convert to TWA with TWA = 16.61×log10(1.164)+90 ≈ 90.8 dB. See Appendix A to 1910.95 for the formulas and tables.

• This example shows combined periods can push dose above 100% even if individual periods are limited.

Appendix A to 1910.95 is mandatory and provides the required computations for determining employee noise exposure (dose and 8-hour TWA). See Appendix A to 1910.95 which is titled "Mandatory" in the appendix heading.

• Use these computations to determine compliance with the exposure limits and required hearing conservation actions in 1910.95.