Noise dose is a percentage measure of your actual noise exposure relative to the maximum permissible exposure. A dose of 100% means you have reached the full allowable daily noise exposure. For example, under EU standards, 8 hours at 85 dBA equals a 100% dose. Any dose above 100% exceeds the permissible limit and indicates a need for hearing protection and noise reduction measures.

What is the difference between EU and OSHA noise standards?

The key difference is the exchange rate and reference level. EU Directive 2003/10/EC uses a 3 dB exchange rate with an 85 dBA reference level, meaning every 3 dB increase halves the permissible exposure time. OSHA uses a 5 dB exchange rate with a 90 dBA reference level, meaning every 5 dB increase halves the time. The EU standard is stricter and more scientifically accurate because the 3 dB rule reflects the actual doubling of acoustic energy.

What is the exchange rate (3 dB vs 5 dB)?

The exchange rate (also called doubling rate or trading ratio) defines how much the noise level must increase to halve the permissible exposure time. A 3 dB exchange rate (used by EU, NIOSH, and most international standards) is based on the equal-energy principle — a 3 dB increase doubles the sound energy. A 5 dB exchange rate (used by OSHA) is more lenient and was historically adopted as a compromise. Most occupational health experts recommend the 3 dB rate as it better reflects hearing damage risk.

What hearing protection should I use?

Choose hearing protection with a Noise Reduction Rating (NRR) sufficient to reduce exposure below 85 dBA. For moderate noise (85–95 dBA), foam earplugs (NRR 25–33) are usually adequate. For high noise (95–110 dBA), combine earmuffs with earplugs (dual protection). For very high noise (>110 dBA), use custom-molded earplugs with maximum attenuation and limit exposure time. Always check the actual attenuation in practice — real-world NRR is typically 50–75% of the rated value.

How is noise measured?

Noise is measured using a sound level meter (SLM) or noise dosimeter. A sound level meter measures the instantaneous sound pressure level in decibels (dB) with A-weighting (dBA) to approximate human hearing sensitivity. A noise dosimeter is worn by the worker throughout the shift and calculates the cumulative noise dose automatically. Measurements should follow ISO 9612 or OSHA guidelines, using slow response time and A-weighting. The microphone should be positioned near the worker's ear.

Free Engineering Tool

Noise Exposure Calculator

Calculate permissible noise exposure time and dose per EU Directive 2003/10/EC and OSHA standards. Enter noise level and exposure duration for color-coded risk assessment.

EU 2003/10/EC OSHA 3 dB / 5 dB Exchange Rate

Results

Permissible Exposure Time

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Noise Dose

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TWA (8-hour equivalent)

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Noise Level

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Standard

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Permissible Exposure Time

The permissible exposure time is calculated from the noise level, a reference level, and the exchange rate:

Noise Dose

The noise dose as a percentage of the permissible limit:

Time-Weighted Average (TWA)

The 8-hour equivalent noise level:

Where:

L — measured noise level (dBA)
L_ref — reference level: 85 dBA (EU) or 90 dBA (OSHA)
ER — exchange rate: 3 dB (EU) or 5 dB (OSHA)
t — actual exposure time (hours)
T_permitted — maximum permissible exposure time (hours)

Practical Example

Example — Worker exposed to 92 dBA for 6 hours (EU standard)

T = 8 / 2^(92−85)/3 = 8 / 2^2.333 = 8 / 5.04 = 1.59 hours

Dose = (6 / 1.59) × 100% = 378%

TWA = 92 + 10 × log₁₀(6/8) = 92 − 1.25 = 90.8 dBA

Risk: Dose 378% > 200% → Danger — immediate action required

⚠️ Note: Maximum permissible time at 92 dBA is only 1 hour 35 minutes under EU standard. Immediate noise reduction measures and hearing protection are mandatory.

Noise Levels of Common Sources

Source	Typical Level (dBA)	Permissible Time (EU)	Permissible Time (OSHA)
Normal conversation	60	Unlimited	Unlimited
Vacuum cleaner	70	Unlimited	Unlimited
Busy traffic / Open office	80	25.4 hours	Unlimited
Factory floor	85	8.00 hours	Unlimited
Hand drill	90	2.52 hours	8.00 hours
Grinding / Power saw	95	0.79 hours	4.00 hours
Circular saw	100	0.25 hours	2.00 hours
Hammer mill / Riveting	105	4.7 min	1.00 hour
Jackhammer	110	1.5 min	30 min
Jet engine (at 30 m)	140	< 0.01 sec	0.07 sec

Permissible Exposure Times by Noise Level

Noise Level (dBA)	EU (3 dB exchange rate)	OSHA (5 dB exchange rate)
85	8 h 00 min	—*
88	4 h 00 min	—*
90	2 h 31 min	8 h 00 min
91	2 h 00 min	6 h 58 min
94	1 h 00 min	4 h 36 min
95	47 min	4 h 00 min
97	30 min	3 h 02 min
100	15 min	2 h 00 min
103	7 min 30 sec	1 h 19 min
106	3 min 46 sec	52 min
109	1 min 53 sec	34 min
112	56 sec	22 min
115	28 sec	15 min

* OSHA reference level is 90 dBA; levels below 90 dBA have no OSHA time limit (PEL not exceeded at 8 hours).

Noise Exposure Calculator — Permissible Time & Dose (EU/OSHA)

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

Results

Permissible Exposure Time

Noise Dose

Time-Weighted Average (TWA)

Practical Example

Noise Levels of Common Sources

Permissible Exposure Times by Noise Level