Case study · Food & drink - A food factory where the plant room was the hotspot
A real, anonymised assessment of a chilled-food factory — where the biggest hearing risk was the refrigeration plant, not the production line.
Impact Acoustics · updated 10 Aug 2026 · 5 min read
The site
A chilled- and frozen-food manufacturer in Cornwall, with Tetra Pak filling lines, a spiral freezer, a mix plant and an ammonia refrigeration plant serving the site. We assessed ten task and area positions on an 8-hour basis, from the factory floor to the plant rooms.
What we found: food factory at 93.9 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.
The three loudest positions were all services plant, not the production line: the ammonia refrigeration plant at 93.9 dB(A), the compressor shed at 87.9 and the mix plant at 85.7 — all at or above the upper action value. The Tetra Pak fillers and both production lines sat in the 81–85 dB(A) band, and goods intake was below the lower action value. No peak reached the 135 dB(C) action value.
The insight that pays for the survey
Two things surprised the site. First, the biggest hearing risk wasn’t on the busy factory floor at all — it was in the refrigeration plant, where the daily dose is so high that a worker reaches the 85 dB(A) upper action value in about an hour of an eight-hour shift, so even short maintenance visits need protection. Second, the loudest single noise on site — a 114 dB(C) peak — was recorded in Packing, which has the site’s lowest daily exposure at 78.9 dB(A). It’s a clean illustration of why a walk-round ‘that sounds loud’ is no substitute for measurement: the area that startles you isn’t always the one damaging hearing over a full day.
What the client got
- Mandatory Hearing Protection Zones at the ammonia plant, compressor shed and mix plant, with access and dwell-time control for maintenance visits.
- Protectors matched to each area by required attenuation (SNR ∼25 at the plant down to lighter protection on the lines), verified so the level at the ear lands in the safe 70–85 dB(A) range.
- A steer to build role-based exposure profiles from real task durations rather than area assumptions, and audiometry for staff regularly in the plant rooms.
- Maintenance flagged as a noise control in its own right — worn bearings, loose panels and air leaks all add decibels.
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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