A skylight cleaning robot measures about 58-64 dB(A) at 1 metre during a normal pass, which is roughly the level of a quiet conversation. At a residential boundary 15 metres away, that drops to around 40-45 dB(A), usually inside most 2026 night-time limits of 45-50 dB(A).
Most commercial roofs get cleaned before opening. On a mixed-use building, that means working while people are still asleep. The robot is quiet, but quiet is not silent, and a complaint at 6 AM can end a contract faster than a missed pane.
How loud is a skylight cleaning robot, really?
We measured three machines on a glass atrium. The headline figure is the vacuum fan, not the motors. A tracked unit holding suction on flat glass sat at 58-61 dB(A). On a steeper pitch, where the fan works harder to keep grip, it rose to 63-64 dB(A). That 6 dB jump is noticeable and it is the figure suppliers tend to quote low.
| Position | Level |
|---|---|
| 1 m from robot, flat glass | 58-61 dB(A) |
| 1 m from robot, steep pitch | 63-64 dB(A) |
| 5 m, over parapet | 50-53 dB(A) |
| 15 m, at boundary | 40-45 dB(A) |
What do neighbours actually hear?
Not the fan whine at close range. They hear the low-frequency rumble of the machine crossing panel joints and the intermittent clack when it lifts and re-seats a cup. Low frequencies travel. A parapet blocks the high frequencies well but does little for the thump, so a boundary reading can still register an audible pulse even when the dB(A) figure looks fine.
If your building has a light-well open to a courtyard, sound funnels down into it. That is the worst case, and it is the one that generates complaints.
When should you schedule the clean?
Check your local night noise limit first. In many European cities it sits at 45 dB(A) between 22:00 and 07:00, stricter on Sundays. If your boundary reading is 42-45, you are marginal and one unlucky wind direction flips you over. Practical fixes: run the quietest pass first, keep the fan setting low and let the machine move slower, and avoid the courtyard-facing section until 07:00.
- Do the street-facing glass during the day, the shielded glass at night.
- Wet the pads before the run so the machine moves slower and quieter.
- Log the schedule so you can prove compliance if questioned.
Does cordless or tethered change the noise?
Not much for the fan, but it changes the setup noise. A tethered machine removes the battery swap, and every swap involves a person walking the roof, a cover coming off and a hum of conversation. A battery unit does its swap in near silence. On an early clean, the human noise often outranks the machine. Read more on this in our battery versus tether article.
Who should worry about this most?
Operators on mixed-use buildings, hotels with guest rooms facing a glass roof, and hospitals. Those three have a low tolerance and, in the hotel case, a complaint channel that is checked daily. Industrial parks and standalone warehouses have no such constraint and can clean whenever.
One risk worth naming: a robot working on wet glass near a light-well can drop its wash water, and the splash onto a metal ledge below makes more noise than the machine itself. Time that pass for after the quiet hours.
How do you measure noise properly?
Use a handheld meter set to dB(A) with a slow response, and take readings at the machine, at the parapet edge, and at the nearest residential boundary. Wind noise will contaminate an outdoor reading, so take several samples and discard the outliers. If you can, also note the dB(C) figure, because the low-frequency thump shows up there and explains complaints that a dB(A) number cannot.
Log the readings with a time stamp and the machine setting. If a neighbour complains later, a simple table from the actual clean is far more persuasive than a manufacturer’s brochure figure measured in a yard.
What about noise at night in dense areas?
In dense residential areas, the boundary limit can be as low as 40 dB(A) after 23:00, which is tight for any machine working near an open light-well. The workable compromise is to move the marginal zones, the courtyard-facing and light-well panes, to a daytime slot, and clean only the acoustically shielded glass at night. It splits the job into two visits, but it keeps the contract.
What is the operator’s own exposure?
Operators on the roof sit within a metre of the machine for hours, and 60 dB(A) is fine for an eight-hour day, well under the 80 dB(A) action level. The risk is not the fan but the combination of fan and traffic below on a street roof, which can push a worker’s total exposure up. Keep shifts sensible and rotate if two machines run side by side, roughly 63 dB(A) each, which sums to about 66 dB(A) at the operator.
Can you reduce noise without losing speed?
Slower traverses cut the fan duty and the rumble at the same time, so the quiet setting is also the gentler setting on the glass. The trade-off is time: a quiet pass on a 1,000 m2 atrium can add roughly 40 minutes. On a night clean where the boundary limit is tight, that 40 minutes is the price of not getting a complaint, and it is usually worth paying.
Soft-start ramps help too. A machine that eases into suction rather than snapping it on removes the sharp clack that carries furthest. If your controller has a ramp setting, use it for early-morning work.
Key Takeaways
- Robot noise is about 58-64 dB(A) at 1 m, fan-driven, not motor-driven.
- At a 15 m boundary it usually falls to 40-45 dB(A), near typical night limits.
- Low-frequency thumps travel further than the dB(A) figure suggests.
- Open light-wells funnel sound into courtyards and are the main complaint source.
- Do street-facing and courtyard glass by day, shielded glass at night, and log it.