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4.3.6 Real World Attenuation Variability

Fit Testing Evidence

  • HSE RR720 demonstrated that real world attenuation is often much lower than laboratory SNR values.
  • Different workers using the same protector can achieve very different levels of protection.
  • Variation arises from ear canal anatomy, fitting technique, and consistency of wear.
  • This variability makes population level assumptions unreliable.

What it is: Real world research, including HSE RR720, has shown that the attenuation workers actually achieve with a hearing protector can vary widely from person to person, even when they are using the same model of earplug.

Why it matters: This variability means that relying on a single SNR value for a whole workforce is unreliable. Some workers may be well protected while others receive far less attenuation than expected. Individual fit testing, which produces a Personal Attenuation Rating (PAR) for each worker, is the only way to account for this variability and ensure everybody is protected to an adequate level.

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