How quiet should a bedroom be for sleep?

A study of 62 adults tracked their own bedrooms for 14 nights. On the noisiest nights, they spent about 4.7% less of their time in bed sleeping than on the quietest nights⁴. That shows two things happening together. It doesn't prove one caused the other. People in that study seemed to get used to their rooms, whatever the levels were, so a noisy room may not feel noisy to you⁴.

People differ a lot here. In a lab study of 69 adults, a large share of the differences in how much noise disturbed people came down to the person, not to age, sex or the study set-up⁵. So a room that's fine for your partner might not be fine for you.

The WHO also has a figure for outside the home: less than 40 dB(A) averaged over the year at night¹. That's an outdoor average, so it can't be compared directly with a reading taken beside your bed.

• Earplugs. In a lab study of 25 adults, foam earplugs removed nearly all the effects of noise that came and went. They started to fall short at the loudest level tested, 65 dBA³. If you need to hear a baby or an alarm at night, they may not suit you. Not for you? That's fine.
• Pink noise machines. These are less clear-cut. In the same study, pink noise cut the dreaming stage of sleep, and the authors caution against using it widely until there's more research³.

Dormio sits by the bed and keeps an eye on the room: fresh air, warmth, humidity, light and sound. For sound, it keeps a level and no audio. It looks at the room, not at you.