Case study · Metal fabrication - A fabrication shop with one 90 dB(A) hotspot
A real, anonymised assessment of a sheet-metal fabricator — one area over the limit, and how to control it without blanketing the shop.
Impact Acoustics · updated 10 Aug 2026 · 4 min read
The site
A sheet-metal fabricator in Dorset, running punch presses, a guillotine, folding and a shaking-out area where finished parts are separated from offcuts. We measured eight areas across the shop and offices to Class 1 standard on an 8-hour basis.
What we found: metal fabrication at 90.0 dB(A)
Real measured daily personal noise exposure (LEP,d) by work area, from an anonymised recent assessment. Values above 85 dB(A) are Hearing Protection Zones.
Only one area crossed the upper action value — the shaking-out area at 90.0 dB(A), a full 5 dB over the 85 dB(A) limit, with peaks of 122.6 dB(C). The punch presses and guillotine sat in the high-70s dB(A), below the lower action value, and folding, coil, welfare and office areas were quieter still. No peak reached the action value.
The insight that pays for the survey
This is the opposite of a whole-shop problem: the risk is concentrated in one area. At 90 dB(A) the shaking-out operator uses up a full day’s noise ‘budget’ in about two and a half hours, so the answer isn’t blanket ear defenders across the factory — it’s a defined Hearing Protection Zone around shaking-out, sensible time-at-task limits and the right protector there. The assessment showed that a correctly-worn SNR 25 protector, realistically de-rated, brings that operator down to about 69.6 dB(A) at the ear — safely below the action value — while the rest of the shop is managed proportionately rather than over-protected.
What the client got
- A single, clearly-marked Hearing Protection Zone around the shaking-out area, rather than blanket signage across a shop that mostly doesn’t need it.
- A protector spec for that area (SNR 25, de-rated) that lands the operator at about 70 dB(A), with time-at-task guidance so exposure stays controlled.
- Information and training for the team, audiometry where appropriate, and a re-measure built in for when plant or layout changes.
That is the difference between a survey that just says “you’re over the limit” and one that tells you exactly where to act — and keeps it current, which is what the 4-Year Care Plan is for.
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