Are Sound Machines Bad for You or Your Baby?

Sound machines are not inherently harmful, but they can become a problem if the volume is too high or the speaker sits too close to a sleeper’s head. Lab testing of popular infant sound machines found that roughly two-thirds exceeded occupational noise-safety thresholds when cranked to maximum volume and placed just a few inches away from a microphone. At moderate settings and reasonable distances, the same devices fell well within safe limits. The real question is not whether you should use a sound machine at all, but how you use it.

Volume and Placement Change Everything

Two separate lab studies have measured the output of commercial infant sound machines under controlled conditions, and both arrived at the same core finding: distance and volume setting determine whether the device is safe or dangerous. A 2021 study tested fourteen devices marketed for infant use and found that at maximum volume and a speaker-to-microphone distance of just 10 centimeters (roughly 4 inches), nine of the fourteen exceeded 85 dBA, the occupational noise limit recommended by the National Institute for Occupational Safety and Health. Move the microphone back to 30 or 100 centimeters and not a single device exceeded that threshold, even at max volume. At minimum volume, none exceeded the limit at any distance.¹

An earlier study from 2014, published in Pediatrics, tested a different batch of infant sleep machines and found that all of them produced levels above 50 dBA at 30 centimeters, which is the recommended noise ceiling for hospital nurseries. Three machines produced output above 85 dBA at that same distance, meaning that running them at full blast near a crib for a typical overnight stretch could exceed the accumulated noise exposure limits set for working adults.² The takeaway from both studies is consistent: a sound machine on a low-to-moderate setting placed across the room, rather than inches from the crib rail, is unlikely to pose a hearing risk. The same machine jammed against the mattress at max volume is a different story.

How White Noise Helps With Sleep

The reason so many parents and adults reach for a sound machine in the first place is that it works, at least for falling asleep. The basic mechanism is straightforward: a continuous sound fills the gaps in background noise, which means that a door closing, a dog barking, or a truck rumbling past is less likely to jolt you awake. Polysomnographic studies have confirmed that adding mixed-frequency white noise to an environment reduces the number of times a sleeper is aroused by sudden peak sounds, because the difference between the baseline noise and the spike is smaller.³

For infants specifically, the evidence for sleep benefits is encouraging. A comprehensive review in the journal Noise & Health found that white noise at safe levels extended sleep duration, improved sleep efficiency, and reduced stress scores in newborns. In premature infants, one study found that sleep duration increased by about two hours in the white noise group compared to the period before the intervention.⁴ That is a meaningful difference for babies in neonatal units, where sleep is frequently interrupted by alarms and medical procedures. For healthy full-term infants at home, the improvements tend to be less dramatic but still real: parents commonly report that their baby falls asleep faster and stays asleep longer.

In adults, results are more mixed. A 12-week trial in hospitalized adults found that the group using white noise showed improvements in how quickly they fell asleep and in overall sleep quality scores compared to a control group.⁵ But a smaller study using overnight polysomnography in healthy adults found no significant changes in total sleep time, sleep efficiency, or sleep architecture between white noise and control nights.⁶ The likeliest explanation for the discrepancy is environment. If you already sleep in a quiet room with few disruptions, adding white noise is adding a new sound rather than masking a problematic one. If your environment is noisy or unpredictable, the masking effect has something to work with.

The Concern About Developing Ears and Brains

Your ears contain a fixed number of tiny hair cells in the inner ear that convert sound waves into electrical signals for the brain. These cells do not regenerate in humans. Damaging them is permanent, and the damage accumulates over a lifetime.⁷ That fact alone explains why pediatricians care about how loud a sound machine is.

But the concern for infants goes beyond raw volume. Animal research has shown that continuous white noise during early development can interfere with how the auditory brain organizes itself. Rat pups raised in moderate-level continuous white noise for the first 50 days of life showed delayed development in the primary auditory cortex. The normal process by which the brain learns to distinguish different frequencies and map sound precisely was delayed past its usual developmental window, and in some cases the critical period for auditory refinement was kept open indefinitely instead of closing on schedule.⁸ A related study found that the same early noise exposure disrupted the normal balance of synaptic strengthening and weakening in the brain’s auditory pathways, essentially leaving the system in an immature state.⁹

These are animal studies, and the exposure was continuous, meaning the noise never stopped. No reasonable parent is running a sound machine 24 hours a day. But the findings are a reason to treat sound machines as a sleep tool, not an all-day background feature. The developing brain needs exposure to patterned sounds like speech, music, and the natural variety of environmental noises to build its auditory map properly. Filling every quiet moment with a wall of undifferentiated sound could, in theory, get in the way of that process.

Infants Already Struggle to Hear Speech in Noise

Even when a sound machine is not loud enough to threaten hearing damage, it still raises the background noise level in a room, and infants are at a built-in disadvantage when trying to pick out meaningful sounds from a noisy backdrop. A study comparing speech detection in infants, children, and adults found that infants needed the signal to be about 24 decibels louder than adults did before they could detect it in background noise.¹⁰ That is a large gap. A sound machine running at a moderate level during waking hours could mean that a baby cannot hear a parent talking from across the room nearly as well as the parent assumes.

This does not mean sound machines harm language development on their own. The research connecting continuous white noise during sleep to speech or learning problems is still preliminary and largely theoretical rather than demonstrated in clinical trials. A 2024 scoping review noted that white noise machines are widely used and may lead to poor hearing, speech, and learning outcomes if used incorrectly, but framed this as a concern warranting further study rather than an established fact. The practical implication is simple: use the machine when the baby is sleeping, and turn it off when the baby is awake and engaging with people and language.

What Higher Sound Levels Do to Your Body Overnight

For adults, the volume dial has consequences beyond hearing. A study examining the relationship between overnight sound levels and sleep stages found that higher average sound levels across the night were associated with less REM sleep, the phase of sleep linked to memory consolidation and emotional processing. A larger number of sound spikes above 60 dB was also tied to reduced REM time.¹¹ In other words, even if you feel like you slept through the night, the quality of that sleep could be diminished if the ambient sound level is creeping up too high.

Short-term noise exposure also nudges the cardiovascular system. A panel study in healthy men found that noise exposure reduced heart rate variability, a measure of how well the autonomic nervous system adjusts to moment-by-moment demands. Low-frequency noise cut certain heart rate variability indicators by roughly a third, while high-frequency noise produced smaller but still measurable drops. Blood pressure and cortisol, interestingly, did not change during these short exposures.¹² The relevance to sound machines is indirect: the noise used in the study was not white noise specifically, and the levels were designed to simulate environmental noise rather than a sleep aid. But it is a reminder that the body registers sound even when you do not consciously notice it, and keeping volumes low matters for reasons beyond hearing protection.

Practical Guidelines for Safe Use

No major health organization has issued a formal dosage recommendation for infant sound machines, but the research points toward a few sensible rules:

Keep it across the room: Place the machine as far from the crib or bed as practical. Even a couple of feet makes a measurable difference in the sound level reaching the ear. The lab studies showed that devices dangerous at 10 centimeters were well within safe limits at 100 centimeters.
Use low-to-moderate volume: If you have to raise your voice to talk over the machine, it is too loud. Many devices have no decibel readout, so a smartphone sound-level meter app can give you a rough check. Aim for something in the range of 50 to 65 dB at the distance where the baby sleeps.
Limit the run time: Using the machine for naps and overnight sleep is reasonable. Leaving it on during all waking hours is not, especially for infants whose brains are actively learning to process speech and varied sounds.
Use a timer if available: Some machines have auto-shutoff features. Turning the sound off after the baby has fallen into a deeper sleep stage means less total noise exposure per night.

For adults, the same principles apply in less urgent form. You are not in a critical period of auditory brain development, but chronic exposure to moderate noise throughout the night can still chip away at REM sleep and hearing over years. A volume that just barely masks the sounds that wake you up is better than a volume that drowns out everything.

Can You Become Dependent on a Sound Machine?

Parents often worry that a baby who learns to sleep with white noise will never learn to sleep without it, and adults wonder the same about themselves. There is no clinical evidence that sound machine use creates a physiological dependency, but a behavioral habit is real. If a child has always fallen asleep with a consistent sound and that sound is suddenly removed, they may have a harder time settling. This is not different from any other sleep association, like being rocked or nursed to sleep. The noise becomes part of the expected conditions for falling asleep.

The practical fix is not dramatic. Gradually reducing the volume over a period of nights is usually enough to break the association. Some parents choose to use sound machines only in noisy environments rather than every night, which naturally prevents the habit from becoming entrenched. The concern is worth noting but not worth losing sleep over, so to speak.

Sound Machines and Tinnitus

One population that benefits clearly from sound machines is adults with tinnitus, the perception of ringing or buzzing that has no external source. Sound generators are a core part of tinnitus management programs, and a study evaluating four different noise types found that all were equally effective in helping patients habituate to their tinnitus, with no statistically significant differences between them.¹³ The mechanism is similar to the sleep-masking effect: by filling the auditory space with an external sound, the brain gradually stops flagging the tinnitus signal as something important. For tinnitus sufferers who also have trouble sleeping, a bedside sound machine serves double duty.

What the Fetus Hears

A question that rarely comes up but has interesting implications: does sound from the outside world reach a developing fetus, and should pregnant people worry about sound machines? A 2025 modeling study in Nature Communications found that sounds below 1 kHz pass through the uterus with very little attenuation, arriving at the fetus at nearly the same level as the incident wave. For low-frequency sounds, the womb offers almost no protection.¹⁴ White noise contains energy across a wide frequency range, including those low frequencies that travel through tissue easily. This does not mean a bedside sound machine at moderate volume is dangerous during pregnancy, but it does mean that the assumption many people make (the baby can’t hear much in there) is wrong for lower-pitched sounds. A pregnant person sleeping next to a sound machine at a reasonable volume is unlikely to cause harm, but someone working in a consistently noisy environment might want to be more mindful than they would otherwise assume.

Fan Noise and SIDS Risk

Many parents use a fan as a low-tech alternative to a sound machine, and one widely cited study gave an unexpected reason to keep doing so. A case-control study found that fan use during infant sleep was associated with a roughly 72% reduction in the risk of sudden infant death syndrome, with the protective effect strongest when the sleep environment was already less than ideal: warmer room temperatures, prone or side sleeping positions, or bed-sharing with someone other than a parent.¹⁵ The researchers attributed the effect primarily to improved air circulation around the infant, not to the sound itself. A fan moves air and reduces the chance of carbon dioxide rebreathing, which is one proposed mechanism in some SIDS cases. A sound machine sitting on a shelf does not move air at all, so the SIDS-protective finding does not transfer to white noise devices. The study is worth knowing about, but it is an argument for ventilation rather than for sound per se.