Hearing Protection Attenuation Calculator

Work out hearing protection attenuation instantly with clear inputs, formula shown and shareable results.

About Hearing Protection Attenuation Calculator

Laboratory noise reduction ratings overstate field performance. For A-weighted measurements seven decibels are subtracted to correct for the C-weighted basis of the rating, then a derating factor of about fifty percent accounts for imperfect fit in real use. The target is to bring the level at the ear to between 70 and 85 dBA.

Formula

Protected level

Level at ear = ambient dBA - (NRR - 7) x derating factor

Worked example

With the default values below, Hearing Protection Attenuation Calculator returns Level at the ear with protection of 91.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Ambient noise levelaccepts 40–140 dBA: 100 dBA
Noise reduction ratingaccepts 1–40 dB: 25 dB
Real world derating factoraccepts 0.1–1: 0.5

Results

Level at the ear with protection: 91.00 dBA
Effective attenuation: 9.00 dB
Derated noise reduction rating: 9.00 dB
Adequacy: Insufficient — select higher attenuation or use double protection

Step by step

1Values used
2Protected level
3Level at the ear with protection= 91.00 dBA
4Effective attenuation= 9.00 dB
5Derated noise reduction rating= 9.00 dB
6Adequacy= Insufficient — select higher attenuation or use double protection

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Preliminary estimate only. Hearing protector selection must follow the manufacturer's octave band data and the derating method required by your regulator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Hearing protector selection must follow the manufacturer's octave band data and the derating method required by your regulator.

Frequently Asked Questions

How is the Hearing Protection Attenuation figure worked out?

Level at ear = ambient dBA - (NRR - 7) x derating factor. Laboratory noise reduction ratings overstate field performance.

Can protection be too good?

Yes. Below about 70 dBA at the ear, speech and alarms become hard to hear and workers remove the protection, which is far worse than moderate attenuation worn consistently.

What values do I need to enter?

This calculator takes 3 inputs: Ambient noise level, Noise reduction rating, Real world derating factor. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.