No health body publishes a limit for sound played all night. The numbers that exist were written for hearing protection: the NIDCD says sounds at or below 70 dBA are unlikely to harm hearing, and NIOSH recommends 85 dBA as the most you should average over an eight-hour workday. We have no level of our own to add, so this article lays out what the sources say and what they leave open. More explainers like it are in our sound science guides.
What do the published limits say?
Two figures come up again and again, and both come from hearing-loss guidance rather than sleep research. The NIDCD says that sounds at or below 70 A-weighted decibels (dBA), even after long exposure, are unlikely to cause hearing loss, while long or repeated exposure at or above 85 dBA can. The louder the sound, the less time it takes to do damage.
NIOSH states its recommended exposure limit for occupational noise as 85 dBA, averaged over an eight-hour shift, with a 3 dB exchange rate. That rate means each 3 dB increase halves the time you should spend at that level.
| Source | Number | What it covers |
|---|---|---|
| NIDCD | 70 dBA | Sounds at or below this are unlikely to cause hearing loss, even after long exposure |
| NIDCD | 85 dBA | Long or repeated exposure at or above this can cause hearing loss |
| NIOSH | 85 dBA | Recommended limit averaged over an eight-hour workday |
| NIOSH | 3 dB | Exchange rate: each 3 dB rise halves the allowed time |
Decibels are logarithmic, so a sound 10 dB louder is ten times more intense. A small turn of the dial is a bigger change in the room than it sounds.
The gap is time. 85 dBA is an eight-hour work number, and a night is a different situation. Take it as a reference point, not a bedroom rule.
What did the studies look at?
The one study that measured the output of sound machines in detail is a device test, and it measured loudness, not sleep. Researchers tested 14 devices, 8 infant white noise machines and 6 phone apps, at their lowest and highest volume. They measured at 10 cm, which stands in for a crib, at 30 cm, just outside a crib rail, and at 100 cm, a nightstand across the room. They used the NIOSH Sound Level Meter app and compared the readings with the 85 dBA threshold.
It says nothing about how anyone slept or how their hearing fared. It tells you how loud the speakers got, and that's all.
What did they find?
Volume and distance both mattered. At minimum volume, no device exceeded 85 dBA at any distance. At maximum volume, 9 of the 14 devices (64.3%) exceeded 85 dBA at 10 cm, while none did at 30 cm or 100 cm. The authors advise avoiding maximum volume and keeping a device at least 30 cm away. The abstract does not report the peak readings themselves.
The AAP offers a simpler check that needs no meter. It says that if an environment sounds too loud for an adult, it probably is too loud for a child, and that "too loud" can mean having to raise your voice to talk to someone an arm's length away. For sound machines, the AAP says it may be safer to place them as far away as possible, set the volume as low as possible and limit how long they run. HealthyChildren.org gives the same advice for parents: keep the machine as far from the baby's head as possible. Neither page gives a decibel number.
What did they not find?
They did not find a limit for sound played all night. None of the pages above names a safe level for sleeping, and the device study did not test adults or full nights.
The World Health Organization's night-noise values are easy to mistake for one. Its 2018 guidelines recommend road traffic noise below 45 dB Lnight, railway noise below 44 dB and aircraft noise below 40 dB, but those are outdoor levels for community noise measured at the building. They do not describe a sound source placed in your bedroom.
Two other things shape how loud a sound feels: its colour and its slope. Our guide to the difference between white, pink and brown noise covers the colours, and what a dB per octave slope means explains how the energy is spread across pitch.
How can you check your own volume?
Start with the arm's length test from the AAP. Sit where you sleep and have someone speak to you, or speak to someone, at arm's length. If you have to raise your voice, the sound is louder than it needs to be.
Then work with the sources' advice on distance and time:
- Put the speaker across the room, not next to your head.
- Set it to the lowest volume that still covers the noise you want to cover.
- Avoid the maximum setting.
- Use a timer or a fade, so the sound does not run at full level for the whole night.
A free sound level meter, such as the NIOSH app used in the device study, can show you a reading in dBA.
Hush Machine, coming to iPhone, makes its noise live on the phone, so nothing loops or repeats, and one dial runs from white noise to deep brown. It has a timer and fade, and nothing leaves the phone. The volume is still yours to set.
Bottom line
No published source sets a limit for sound played all night. The 70 and 85 dBA figures are reference points from hearing-loss guidance, not bedroom rules. What the sources do agree on is practical: keep it quiet, keep it away from your head, and don't leave it at full volume.
If you have concerns about your hearing, talk to a doctor or an audiologist.
Questions
- Is 85 dBA the safe level for sleeping?
- No. NIOSH's 85 dBA is a recommended limit for an eight-hour workday, written for workplaces. It is not a bedroom guideline, and no health body has published a limit for sound played during sleep.
- How loud is too loud for a sound machine?
- Published sources give no number for sleep. The AAP's rule of thumb is that if an environment sounds too loud for an adult, it is probably too loud for a child, and that too loud can mean having to raise your voice to talk to someone an arm's length away.
- Does distance from the speaker matter?
- Yes. In a study of 14 devices at maximum volume, 9 exceeded 85 dBA at 10 cm, and none did at 30 cm or 100 cm.
- What about babies?
- The AAP says it may be safer to place a sound machine as far from the infant as possible, set the volume as low as possible and limit how long it runs. We give no decibel level for a nursery.