Night skylight robot cleaning is usually limited to 45 to 55 dB measured at the nearest residential facade. Vacuum pumps and high-speed brush motors are the loudest parts of a machine, typically 65 to 75 dB one metre away. Because sound drops about 6 dB per doubling of distance, a robot 20 metres from a bedroom window that reads 70 dB on the roof lands near 44 dB at the window. That margin decides which machines can run after 22:00.
Most cities set a night limit somewhere in the 45 to 55 dB band for residential zones. Some are stricter on paper than in enforcement, but a single complaint can shut your night window for months.
What makes a robot loud?
Three sources dominate. The vacuum pump generates a continuous hiss as it holds suction. The drive motors add a lower hum. The brush and squeegee produce an intermittent scraping that carries oddly well at night when ambient noise drops.
- Vacuum pump: 65-75 dB at 1 m, continuous.
- Drive motors: 55-65 dB, steady hum.
- Brush and squeegee: 50-60 dB, intermittent.
- Water pump and spray: 45-55 dB, brief.
Because the numbers stack, a robot rated 70 dB may hit 76 dB with everything running. That is the figure to test, not the idle rating.
How do you plan around a noise limit?
| Measured at roof (1 m) | Distance to window | At window (approx) |
|---|---|---|
| 70 dB | 10 m | 50 dB |
| 70 dB | 20 m | 44 dB |
| 75 dB | 20 m | 49 dB |
| 75 dB | 40 m | 43 dB |
The maths is rough, since buildings reflect and channel sound. It is enough to see that a 75 dB machine needs real distance, or a daytime slot.
Should you clean at night at all?
Sometimes yes. A mall with no residential neighbours can run night cycles freely, and night work avoids tenant disruption during business hours. But a building beside apartments should think twice. The quieter option is an early-morning start, say 05:00 to 07:00, in the gap between residential quiet hours and the start of operations. Check your local ordinance, as some define night as 22:00 to 07:00.
A key risk is that noise rules are enforced by complaint, not patrol. One irritated neighbour changes your schedule more than any regulation. Pre-empt it by notifying residents before the first night clean and running the quietest settings.
Who should not plan night cleaning?
Buildings within 15 metres of residential units, hospitals, or hotels. The margin is too thin, and the reputational cost of a noise dispute outweighs the schedule benefit. For those sites, run daytime or shoulder-hour cleaning with quieter machines and accept slower progress. Modern units used near sensitive buildings, like those in the Lingyun Y3 range, often let you cap pump speed to trade suction margin for a few decibels. Read more in our earlier noise notes and ask our team about measured noise levels before you commit.
Key Takeaways
- Night limits usually fall at 45-55 dB measured at the nearest residential facade.
- Vacuum pumps top the noise list at 65-75 dB at one metre, running continuously.
- Sound drops about 6 dB per doubling of distance, so 20 m buys roughly 6-8 dB.
- Rules are enforced by complaint; one annoyed neighbour can kill your night window.
- Sites within 15 m of homes, hospitals, or hotels should clean by day.