Case study: a production line running at 94 dB(A)

The site

A manufacturing and production facility in the South West of England, running two parallel robot-assisted production lines with a making area, a washroom / clean-in-place (CIP) area, packing stations and a warehouse. We measured eight fixed operator positions to Class 1 standard (BS EN ISO 9612) on a normal production day, and calculated each group's daily personal noise exposure, L_EP,d, on the HSE exposure-points method.

What we found

Three positions sat at or above the 85 dB(A) upper action value — Robot line 1 at 94.0 dB(A), the Washroom/CIP at 91.7 dB(A) and Making at 88.5 dB(A) — making hearing protection mandatory, with health surveillance (audiometry) required for the people who work them. Robot line 2 sat at 83.7 dB(A), between the lower and upper action values, so protection is made available there. Packing and the warehouse were comfortably below the lower action value. No peak reached the 135 dB(C) action value (the highest was 125.4 dB(C)).

The insight that pays for the survey

The two robot lines are, on paper, identical — yet Line 1 measured 94.0 dB(A) and Line 2 measured 83.7 dB(A). That 10 dB gap is the whole story: it means Line 1's noise is not inherent to the process — a quieter version of the same line already exists a few metres away. So the priority action isn't “issue more ear defenders”; it's to find what's different about Line 1 (tooling, guarding, a worn bearing, a panel resonating, a pneumatic exhaust) and bring it back to Line 2's condition. That single fix removes far more exposure than PPE ever could, and Line 2 is the built-in benchmark to prove it worked.

What the client got

• A prioritised action plan: engineering review of Robot line 1, the Washroom/CIP and Making first, using Line 2 as the target condition.
• Mandatory Hearing Protection Zones defined at the three loudest positions, with the right protector spec (a nominal SNR 17 dB protector brings the level at the ear into the safe 70–80 dB(A) range — not over-protected, so people can still hear warnings).
• Health-surveillance (audiometry) set up for the regularly-exposed staff, and a verification survey booked for after the engineering changes, so reductions are proven with measurements rather than assumed.

That is the difference between a survey that just says “you're over the limit” and one that tells you exactly where to spend money for the biggest reduction — and keeps it current, which is what the 4-Year Care Plan is for.