EN-05Environmental & Occupational Noise
Noise Dose & Daily Exposure
OSHA and NIOSH dose, TWA and the EU daily exposure level L_EX,8h for a working shift.
Exposure periods
Period 1
dB(A)
h
Period 2
dB(A)
h
Period 3
dB(A)
h
Total time: 8.00 h
OSHA dose90 dB / 5 dB
NIOSH dose85 dB / 3 dB
OSHA TWA
86.5dB(A)
NIOSH TWA
87.9dB(A)
EU L_EX,8h
87.9dB(A)
L_EX,8h ≥ 87 dB(A): EU exposure limit value exceeded (taking hearing protection into account). Immediate action required.
Permissible exposure time
OSHA PELNIOSH RELYour periods
§ Theory of operation
Equal-energy and exchange rates
Noise-induced hearing loss depends on both level and duration. Regulations trade one against the other using an exchange rate: the level increase that halves the allowed time.
- NIOSH REL and EU / ISO 1999: 85 dB(A) for 8 h, 3 dB exchange; a pure equal-energy rule.
- OSHA PEL (USA): 90 dB(A) for 8 h, 5 dB exchange. Levels below 80 dB(A) are ignored for dose (the 80 dB threshold of the hearing-conservation amendment).
\begin{aligned} \text{Permissible time:}\quad T &= 8\,/\,2^{(L - L_c)\,/\,\mathit{ER}} \quad \text{hours} \\ \text{Dose:}\quad D &= 100 \cdot \sum C_i\,/\,T_i \qquad \% \end{aligned}
where C_i is the actual time at level L_i. A dose of 100 % means the limit has been reached.
Time-weighted average
\begin{aligned} \text{OSHA:}\quad \mathit{TWA} &= 16.61\,\log_{10}(D/100) + 90 \\ \text{NIOSH:}\quad \mathit{TWA} &= 10\,\log_{10}(D/100) + 85 \end{aligned}
EU daily exposure L_{\mathrm{EX},8\mathrm{h}}
Directive 2003/10/EC normalises the energy of the whole working day to 8 hours:
L_{\mathrm{EX},8\mathrm{h}} = 10\,\log_{10}\!\left[\, \sum (t_i\,/\,8\ \mathrm{h}) \cdot 10^{L_i/10} \,\right]
| EU threshold | L_EX,8h | Peak |
|---|---|---|
| Lower exposure action value | 80 dB(A) | 135 dB(C) |
| Upper exposure action value | 85 dB(A) | 137 dB(C) |
| Exposure limit value (with HPD) | 87 dB(A) | 140 dB(C) |
This calculator is an educational aid. Formal assessments require calibrated dosimetry and the procedures of ISO 9612 or OSHA 29 CFR 1910.95.