2.1.1 L108 Guidance on Real-World Protection & De-Rating (Appendix 1)

Appendix 1 of L108 provides methods for estimating the noise reduction from hearing protectors. Crucially, it acknowledges the discrepancy between laboratory data and real-world performance (Health and Safety Executive, 2021).

HSE Recommendation on De-Rating:

"There can be a difference between manufacturers data and real-world protection due to factors such as poor fitting or interference from spectacles or other PPE. HSE recommends that ",

"text4 dB be regarded as an appropriate factor to bridge the gap between manufacturersâ data and real-world factors",

". You should account for this real-world protection. You can do this by adding 4 dB to allow for real-world protection as described below for your chosen method. In this way you will get a better indication of the protection that users are most likely to get and can select appropriate hearing protection accordingly.\" (L108, Appendix 1, Para 11)",

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" Calculate the A-weighted sound pressure level at the ear (L’A) using the formula SNR`. Then, add 4dB to the result. `Realistic L'A = (LC - SNR) + 4dB`.",

"text": " Calculate the Predicted Noise Level Reduction (PNR) and then the L'A. Add 4dB to the result.",

"Octave-Band Method:",

"Calculate the L'A using the full octave-band method. Add 4dB to the result.",

" "Why it matters for fit testing:",

" The HSE's formal recommendation to de-rate manufacturer data by 4dB is an explicit acknowledgement that laboratory values are not reliable in practice. This provides a strong regulatory justification for implementing fit testing, which replaces this estimation with a precise, individual measurement (PAR), eliminating the need for de-rating and providing a more accurate and defensible assessment of protection. Related: [#evidence-real-world-variability](#evidence-real-world-variability), [#ukhca-par-definition](#ukhca-par-definition).",

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