Post-occupancy surveys have been asking the same questions for forty years, and the results barely move. Temperature complaints come first and are largely unfixable in a mixed population. Noise comes second and is entirely a design outcome.
Yet acoustics arrives in most workplace projects as a consultant’s report near the end, after the plan that determined the answer has been fixed.
The distraction distance nobody quotes
There is a useful number in workplace acoustics that almost never appears in a brief: the distance at which a conversation stops being intelligible.
In a typical open plan with a hard floor, an exposed soffit, and no screens, speech remains intelligible at 12 metres or more. Intelligible speech is the specific thing that breaks concentration — not volume. A loud but unintelligible background is measurably less disruptive than a quiet, clear conversation two desks away.
Bringing that distance down to 5 or 6 metres is achievable and involves three moves, none of them glamorous: absorption overhead, absorption or mass between people, and a background sound level high enough to mask the tail of a conversation. Get those and the same plan with the same density becomes usable.
What open plan actually promised
It is worth being fair about the history. Open plan was not sold as a cost saving, at least not originally. It was sold on communication: fewer walls, more overheard useful information, faster decisions.
That claim is partly true and it has a cost the pitch omitted. The same absence of walls that lets you overhear something useful lets you overhear everything else, and human attention does not have a filter for relevance in advance. The research since has been fairly consistent: open plans increase incidental interaction and decrease sustained concentration, and the balance of those two depends entirely on what the work is.
Which means the honest question is not “open or cellular.” It is what proportion of the work in this organisation is interruptible.
The shape that works
The plans that survive contact with occupants tend to share a structure, and it is not a single condition applied everywhere.
- A quiet zone with a real acoustic separation — a door, not a screen — sized for perhaps 20 to 30 per cent of the headcount and bookable by the half day.
- An open area with genuine absorption, tuned for a distraction distance under 6 metres, where the default is quiet conversation rather than silence.
- Enclosed rooms for calls, at a ratio of roughly one per eight to ten desks. This number is consistently underprovided and is the single most common post-occupancy complaint in hybrid workplaces.
- One social space where noise is expected and permitted, positioned so that nobody has to walk through the quiet zone to reach it.
The circulation point at the end matters more than it sounds. A plan where the route to the coffee passes the concentration area has an acoustic problem no material specification will solve.
The number to ask for How many enclosed call spaces per desk? If the answer is below one in twelve, the project has designed a building where people take meetings in stairwells.
Materials, briefly
The acoustic toolkit is small and well understood, and it is worth knowing what each element actually does.
Ceiling absorption reduces reverberation and the general level — it lowers the noise floor. Screens and furniture block the direct path between two people — they reduce intelligibility at short range. Soft floors deal with footfall and chair scrape, which is impact noise and unrelated to speech. Background sound systems raise the masking level and are the most contested element, because they work and many occupants dislike being told they are being masked.
The order of effectiveness per unit cost is roughly: ceiling, floor, screens, masking. The order of installation on most projects is the reverse, because screens and masking can be bought after handover and a ceiling cannot.
That sequencing, not any failure of acoustic science, is why so many offices are hard to work in. The decisions that matter were made when the drawing said “open plan” and nobody asked what would be audible from where.
