Guide · Reading the map correctly - What a noise floor map does — and doesn't — prove
A measured or predicted sound-level map is one of the clearest ways to see where noise sits across a space. It’s also easy to over-read. Here’s exactly what it shows, and what it can’t.
Impact Acoustics · published 22 Oct 2026 · 5 min read
A floor map takes sound levels — measured at real points, predicted between them, or modelled from equipment data — and turns them into a picture you can read at a glance. That’s genuinely useful. It’s also exactly the kind of output that gets over-read if the labels and the limits aren’t spelled out alongside it.
What it actually shows
- A snapshot, not a certificate. Every map is tied to the conditions it was captured under — which machines were running, in what state, on what day. It shows what the floor looked like then, not a permanent guarantee of what it looks like now.
- Three different kinds of point, not one. A good map distinguishes measured points (taken on site with a calibrated meter), interpolated areas (estimated between measured points), and predicted zones (modelled from equipment or layout data rather than measured directly). Colour and shading carry meaning — they’re never decoration.
- Area or task-level sound levels — what the space itself sounds like — which is a different quantity from an individual’s personal exposure over a working day, and different again from their exposure after hearing protection. A map answers the first question; it doesn’t answer the other two on its own.
What it does not prove
- It isn’t a legal pass or fail. A map doesn’t certify compliance with the Control of Noise at Work Regulations 2005, and no area on it should be read as simply “safe” or “unsafe” — that judgement depends on exposure duration, protection worn, and a competent assessor’s interpretation of the full picture, not a colour on a plan.
- It doesn’t account for what hasn’t happened yet. A new machine, a moved partition, or a changed shift pattern can shift the whole picture — see what actually triggers a review. The map is only as current as its own capture date.
- It doesn’t replace a full noise risk assessment. The map is a visual layer on top of the real assessment — the written report, the measured exposure figures, the action points — not a substitute for it.
- It doesn’t certify hearing protection adequacy. Whether a given protector is adequate for a given role depends on its attenuation rating against that role’s actual exposure, which is a separate calculation the map alone can’t carry.
How to use it correctly
Read the map alongside the written assessment it came from, not instead of it. Check the capture date and the conditions it was taken under. Treat measured points as more certain than interpolated or predicted ones, and treat the whole thing as a live document that goes stale the moment something real on the floor changes. If a site change happens between visits, that’s a reason to report it through your Care Plan rather than wait for the map to catch up on its own — between visits, your record stays current because you tell us what’s changed, not because anything is watching the floor in real time.
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