Sound machines have become standard equipment in a way they were not twenty years ago, and mostly for good reason. But they get used as a general-purpose sleep fix when what they actually do is quite specific: they mask variation.
That distinction matters, because it tells you when a sound machine will help enormously and when it will do nothing at all.
What sleep sounds actually do
A child does not usually wake because a room is too quiet. They wake because something changed — a door, a car, a sibling, a floorboard, the boiler. Continuous sound raises the noise floor so that those changes are less distinct against the background.
If your child's sleep is being broken by intermittent noise, a sound machine is close to a miracle. If your child cannot fall asleep because they are anxious, over-tired, or under-tired, it will not help, and layering one on top will just add a variable.
The types, briefly
White noise
Equal energy across all frequencies. Sounds like an untuned radio or a harsh hiss. Very effective at masking, but many people find the high-frequency content unpleasant.
Pink noise
Energy falls as frequency rises. Sounds like steady rain or wind in trees. Warmer than white noise and generally better tolerated. This is what most people actually want when they say "white noise."
Brown noise
Falls off more steeply again. A deep rumble, like distant surf or a waterfall heard through a wall. Good for masking low-frequency intrusions like traffic and bass from a neighbour's television.
Nature sounds
Rain, streams, waves. These work well provided they are genuinely continuous. Avoid any recording with events in it — a seagull, a thunderclap, a car passing in a "city rain" track. An event is exactly the thing you are trying to mask.
Heartbeat and womb sounds
Popular for newborns. There is nothing magic about them beyond being low-frequency and continuous, and most babies transition off them without difficulty.
Music and stories
Different category entirely. Music with structure — melody, verses, a build — keeps the brain engaged and following. It is fine for the settling-down part of the evening and less good for staying asleep. If you use audio stories at bedtime, use a sleep timer so it stops rather than running all night.
Volume: the part that matters most
This is the one genuinely safety-relevant decision, and it is easy to get wrong.
- Keep it at or below about 50 decibels — roughly the level of a quiet conversation or a fridge hum.
- Put the machine across the room, not in the cot and not on the headboard. Distance is the easiest way to control exposure.
- Test it at the child's ear, not from where you are standing.
- If you have to raise your voice to be heard over it, it is far too loud.
Sound at the child's ear for eight to ten hours a night is a long exposure. The instinct to turn it up to cover a specific noise is understandable and should be resisted; move the machine or address the noise instead.
Continuous, not looping badly
Cheap machines and free apps often loop a short sample, and the seam is audible — a small click or a repeated bird every 30 seconds. Once you notice a loop you cannot un-notice it, and neither can a child.
Look for genuinely generated noise, or long recordings with a clean loop point. Test it yourself by lying in the dark and listening for two minutes.
Should it run all night?
Two reasonable positions:
All night. The most common approach and the most effective for masking. The argument against — that a child becomes dependent — is largely overstated; it is a sleep association like a dark room or a duvet, and nobody worries about duvet dependency.
Timer. Useful if the machine is only helping with the falling-asleep part, or if you would rather hear your child clearly overnight.
The one thing to avoid is having it stop partway through the night on a schedule. The sudden absence of sound is itself a change, which is the thing you were trying to prevent.
When you want to stop using one
Holidays, moving house, or just preference. It is not difficult:
- Reduce the volume slightly every few nights over two or three weeks.
- Keep everything else in the bedtime routine identical.
- Expect a few disrupted nights in the middle and hold the course.
Doing it gradually matters far more than the total time it takes.
What to use instead of a machine
You do not need a dedicated device. A fan works well and has the advantage of being genuinely continuous and slightly cooling. An air purifier does the same job. Both are less likely to be too loud than a purpose-built machine with a volume dial.
When sound is the wrong tool
Be honest about the problem you are solving:
- Frightened of the dark, or of being alone? A sound machine will not touch this. Reassurance, a nightlight, and daytime work will. See helping kids with nightmares.
- Not tired? Look at nap timing, wake time, and how much daylight and physical activity they got.
- Fighting the routine? That is a boundary question, not an audio one.
- Waking at the same time every night? Often a temperature, hunger, or sleep-cycle issue rather than noise.
A sound machine is a good tool with a narrow job. Used for that job it is excellent, and it is one of the cheapest improvements available to a household with thin walls or a street outside.