Why volume and distance matter

Two things decide how much sound reaches your ears, how loud the machine is, and how far away it is.

In a lab test of common infant sleep machines, researchers measured sound at different distances. At just 30 centimetres, which is roughly “on the crib rail”, every device exceeded 50 dBA, and a few hit 85 dBA or more at max volume. That is the kind of level adults get warned about in occupational safety rules if exposure is long. When the devices were moved out to 100 and 200 centimetres, the levels dropped a lot.

At the same time, big health bodies that care about sleep, like the World Health Organization, aim for around 30 dBA indoors at night for good sleep quality. Not absolute silence, but a genuinely quiet bedroom. That is the background you are trying to protect, while using sound machines to smooth out unavoidable peaks.

Infants and children are more vulnerable to noise than adults. They cannot move away or turn the volume down for themselves, and their ears are still developing. That is why paediatrics groups talk not just about loudness but about dose, the combination of level multiplied by time. Short bursts of moderate noise are very different from eight hours a night of high volume next to the crib.

For adults, the goal is different, you are usually using a sound machine to create gentle masking. You want the room to feel calmer and more predictable, not like a jet engine or a thunderstorm on loop.

So the core rules are simple,

• keep the machine as far away as is practical,

• keep the volume as low as still effective,

• and remember that time matters as well as volume.

Practical targets, infants versus adults

Let us turn that into numbers you can actually use.

For infants and toddlers, 0 to 24 months

When you think about a safe decibel level for a baby sound machine, think conservative. Your priorities are hearing safety first, soothing second.

• Volume at the crib, aim for 50 dBA or less
  Use an A weighted meter (more on that below) at the crib edge or roughly where your baby’s head is.
  If you can settle your baby at 40 to 45 dBA, even better.

• Distance, about two metres or seven feet away
  Put the machine on a shelf or dresser across the room, not on the crib rail, not hanging on the bars, not right next to the mattress.
  If the room is very small, still aim for “as far as you can” and adjust volume downward.

• Duration, shortest that still works
  You might use sound for the first 20 to 60 minutes to help settling, then use a timer or reduce volume once your baby is deeply asleep, especially if you needed a slightly higher level to begin with.
  In noisier homes you may choose to run sound longer, just remember that level times time is what matters.

• Other noises, count the whole picture
  Fans, HVAC, TVs in the next room, they all add to the overall background. The quieter everything else is, the less you need from the sound machine.

If you are ever unsure, you are allowed to ask your paediatrician specifically about sound machines and hearing. You do not have to guess alone.

For adults and older kids

Adults have tougher ears and more control over their environment, but sleep still prefers quiet.

A realistic zone for white noise safe decibel sleep looks like this:

• Volume at the pillow, roughly 30 to 45 dBA
  Measure at the spot where your head rests.

  • Around 30 to 35 dBA feels like a very quiet room with a soft texture on top

  • Around 40 to 45 dBA feels a little more present, useful if you are masking city traffic or snoring

The target is not “as loud as possible until I cannot hear anything else”. It is, “quiet enough that small sounds do not keep pulling me up through the sleep stages”.

Tinnitus specific

If you have tinnitus and you are using a sound machine for relief at night, the target is slightly different:

• Set the volume just below your tinnitus, so you can hear both the sound and the ringing

• That is how most habituation based tinnitus therapies work, your brain gradually learns that the ringing is unimportant background

Cranking the sound up to completely drown tinnitus often backfires, because it demands higher levels and can make the silence in between sessions feel even starker.

What “dBA” means, and why decibels are weird

Decibels are not a normal scale. They are logarithmic, which means that a small change in number can represent a big change in energy.

Two quick translations,

• an increase of 3 dB is roughly a doubling of the sound energy at the ear

• an increase of 10 dB is what most people perceive as “about twice as loud”

The “A” in dBA stands for A weighted, a filter that roughly matches how human ears respond to different frequencies. That is why you will see A weighted decibels recommended for environmental and sleep related noise, they map better to what we actually hear.

So when you are checking white noise safe decibel levels for sleep, you want dBA, not just dB, and you want to be aware that a jump from 40 to 50 dBA is not a tiny change, it is a lot more sound energy.

How to measure sound machine levels with a phone

You do not need pro audio gear to do this, a phone plus a decent app is usually enough to get in the right ballpark.

Step 1, Pick an A weighted meter app

• On iOS, the NIOSH Sound Level Meter app tends to be the gold standard, it has been lab tested and comes reasonably close to professional meters if you use it correctly.

• On Android, accuracy varies more between devices, but a well reviewed sound meter app that offers A weighting and shows an average or Leq reading is still better than guessing.

Step 2, Set up as if you were sleeping

• Place the sound machine where you normally would, across the room from the crib or bed

• Set the sound you actually plan to use, white noise, pink noise, rain, fan, at the volume that feels right to you

• For babies, stand with the phone at crib height, near where the head would be

• For adults, put the phone on the pillow where your head goes, mic unobstructed

Step 3, Take a short reading

• Open the app, choose A weighting, and check that it shows an average

• Hold the phone still for 30 to 60 seconds and watch the number settle

• Note the average level, not just the highest blip

If it is higher than the targets we discussed, lower the volume a notch, or move the device farther away, then repeat the measurement. If it is comfortably under, you are done.

Remember, different sounds on the same machine can have different levels, even at the same volume setting, so it is worth checking a couple of favourites.

Placement and setup tips that matter more than brand

You do not need a special “baby sound machine” or a luxury white noise box to be safe. The way you place and use it matters more.

• Across the room, not on the bed or crib
  Doubling the distance from the ear can meaningfully drop the decibel level. For infants, start around two metres if the room allows it.

• Angle the speaker away slightly
  Pointing the speaker directly at the sleeper can concentrate sound. A slight angle away still fills the room without blasting one ear.

• Choose steady sounds
  For sleep, pick broadband sounds (white noise, pink noise, brown noise) or soft, repetitive nature sounds. Avoid tracks with sharp birds, sudden thunder, big ocean crashes, those spikes can wake you even at lower averages.

• Timers and auto off for infants
  For babies, favour options that allow timed runs. You can use higher volume for a shorter time to settle, then let it shut off or switch to a much lower setting.

• Measure new setups
  If you move furniture, change rooms, or buy a new machine, re check levels. Tiny layout changes can alter how sound bounces around the room.

Special notes for caregivers

If you are caring for an infant or a child, you probably have a few extra questions.

Is it ever okay to go above 50 dBA at the crib.
Life is not a lab. In a very noisy building or household, you might need slightly higher volume for short periods to actually mask disruptive noise. If that happens:

• Keep the device as far away as possible, not closer

• Think in terms of shorter runs, for example, a louder setting for the first 20 minutes, then lower or off

• Consider reducing other noise sources too, TV volume, doors, conversations near the bedroom

What if I am worried about my child’s hearing.
Trust that instinct. If you notice your child reacting oddly to sound, needing the TV louder, or if you have had long periods of high volume exposure from toys, venues, or devices, mention it to your paediatrician. They can arrange a hearing check and give more tailored advice.

Can I use a fan or purifier instead of a sound machine.
Yes. Many people use a fan or air purifier as a kind of built in white noise source. Just measure those too, some fans are surprisingly loud on high settings. The same decibel targets apply.

FAQ, quick answers

What is a safe decibel level for a baby’s sound machine.
Aim for 50 dBA or less at the crib, measured at your baby’s head height, with the machine roughly two metres away, and use the lowest volume that still works.

How loud should my sound machine be for adult sleep.
For most adults, the sweet spot is around 30 to 45 dBA at the pillow. Loud enough to smooth out sudden noises, quiet enough that it does not become its own problem.

Can I trust a phone app.
A good A weighted meter app on a modern phone gives a usable estimate. Treat it as guidance, not exact truth, and err on the side of lower volume if you are unsure.

If I have tinnitus, should I turn the sound up until I cannot hear it.
Usually no. For tinnitus sound therapy, a common approach is to set sound just below tinnitus level, so your brain hears both and gradually learns to treat the ringing as background.