How to Choose Hearing Protection — SNR, HML & Octave Band Methods

Choosing the correct hearing protector requires matching the HPE attenuation to the noise levels workers are exposed to. There are three accepted methods: SNR, HML, and the Octave Band method.

SNR Method (Simplest)

Single Number Rating — uses one attenuation value. Appropriate for a rough check only. Subtract the SNR from the measured C-weighted noise level (LCeq) to estimate the A-weighted level at the ear.

HML Method (More Accurate)

Uses three attenuation values — High (H), Medium (M), Low (L) — matched to the spectral character of the noise. More accurate than SNR when noise characteristics are known.

Octave Band Method (Most Accurate)

Uses the full octave band spectrum of the noise and the HPE's attenuation in each band. Required when noise character is unusual or when precise compliance verification is needed.

General Principles

• Target: residual noise level at the ear should be 70–75 dBA (avoid over-protection)
• Over-protection creates communication and safety hazards
• Comfort and wearability are as important as attenuation for compliance

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