Most people turn on a sound machine at bedtime because to them it brings comfort. The sound feels like an easy fix for restless nights, and the instant sense of calm makes it even more tempting to depend on night after night. But does that comforting hum actually improve your sleep — or is it secretly working against the brain repair you’re trying to achieve?
A recent study offers a wake-up call: Apparently, sound machines may lead to a noticeable drop in rapid eye movement (REM) sleep. To put it simply, the nighttime sound that seems soothing might actually be pressuring your brain to work through constant auditory input instead of repairing itself.
These findings challenge the assumption that any calming sound is automatically helpful and set the stage for a deeper look at how sound machines might be working against the very sleep quality you’re trying to protect. Before we go into the findings of the study, let’s briefly discuss how sound machines work.
A Primer on Sound Machines
Sound machines are devices designed to produce a steady stream of background noise that help “fill in” the silence of a room. Many people use them as part of a nighttime routine, especially in environments where sudden or unpredictable sounds may interfere with rest. Rather than relying on a phone app — which can introduce disruptive blue light — sound machines offer a dedicated way to create soothing audio throughout the night.
• Why does a sound machine affect your sleep quality? The answer lies in how the brain processes noise. The fact is that even when you’re at rest during deep sleep, your brain still continues to register noise all around you. Unexpected sounds such as traffic, snoring, pets moving around, or household creaks can trigger brief awakenings or shifts between sleep stages, even if you don’t fully remember waking up.
• A sound machine helps reduce the impact of these disruptions — It provides a stable auditory backdrop. The steady hum it emits smooths out the chaos of a noisy house, an anxious mind, or the unpredictable sounds of cars passing by on the street.
• Sound machines may include a variety of sound options — Some play nature sounds, like rainfall, thunderstorms, beach waves, or frogs at night. Others play white noise, which resembles static and contains all audible frequencies at equal intensity. There’s also what’s called pink noise, which is a softer, deeper static sound that resembles steady rushing water. White and pink noise, along with other types like brown and blue, are also referred to as broadband noise.1
Most research suggests that sound machines are generally safe. Even the National Sleep Foundation (NSF) recognizes that sound machines or “sound conditioners,”2 can help both adults and newborns sleep more soundly. However, if used improperly, pink noise machines may not be completely harmless.
What Does the Newest Research Actually Say About Pink Noise and Sleep?
A more recent report published in the journal Sleep provides more insight into how sound machines may be unknowingly harming your nighttime slumber. Conducted by researchers from the University of Pennsylvania Perelman School of Medicine, the study looked at how different noise conditions, including pink noise, shaped the way the brain moved through deep sleep and REM sleep during the night.3 According to an article from Science Daily:
“During a typical night, the brain cycles repeatedly through deep sleep and REM sleep. Deep sleep plays a key role in physical recovery, memory processing, and the removal of waste products from the brain. REM sleep, often referred to as dream sleep, supports emotional regulation, motor skill development, and brain growth.”4
The researchers’ goal was to understand whether the sounds many people rely on each night improve sleep architecture (the natural structure and cycling of your sleep stages) or disrupt it in ways most users never notice.
• The study followed 25 healthy adults, ages 21 to 41, in a controlled sleep laboratory — Most of them were women, and none had any sleep disorders or had previously used sound machines. For seven consecutive nights, they slept for eight hours, from 11 p.m. to 7 a.m.
• The participants were exposed to different conditions — As they slept, they were placed under varying noise conditions, such as environment noise (sounds of aircraft, cars, baby crying, and alarms), pink noise alone, a combination of environment and pink noise, and environment noise while wearing earplugs.
There were also participants who were allowed to sleep in a quiet environment without any noise exposure (the control group). The researchers used overnight polysomnography, which is considered the gold standard for sleep measurement, to capture the data. This is a comprehensive overnight test that measures brain waves, oxygen levels, heart rate, and eye movements.
• As expected, environmental noise significantly reduced deep sleep and increased nighttime awakenings — The participants exposed to this type of noise lost an average 23 minutes of “N3” deep sleep (considered the deepest and most restorative sleep stage) per night. Even if they didn’t remember waking up in the middle of their slumber, their brain activity reflected shallower, more disrupted sleep. They also felt more tired, stressed, and mentally drained the next morning.
• But what was surprising was the effect of pink noise on deep sleep — Pink noise alone, which was played at 50 dB (imagine the sound of moderate rainfall), caused a significant reduction in REM sleep — nearly 19 minutes of sleep lost per night. Over a week, that’s more than two hours of REM sleep lost.
According to the researchers’ findings, this type of noise interferes with the brain circuits that normally allow REM sleep to begin and continue, so instead of creating a restful background for sleep, it may act as a continuous stimulus that alters the brain’s ability to cycle naturally into REM. Your brain doesn’t fully “turn off” during sleep — it still monitors your environment. Pink noise may keep the auditory processing centers partially active, preventing the full transition into REM.
• Why disrupted REM sleep has a significant effect on your health — Chronic REM deprivation doesn’t just make you tired; it also impairs emotional regulation, weakens memory consolidation, and may even accelerate cognitive decline over time. Mathias Basner, M.D., Ph.D., professor of Sleep and Chronobiology in Psychiatry and the study lead author, explained:
“REM sleep is important for memory consolidation, emotional regulation, and brain development, so our findings suggest that playing pink noise and other types of broadband noise during sleep could be harmful — especially for children whose brains are still developing and who spend much more time in REM sleep than adults.”5
What’s even more damaging was when pink noise was combined with environment noise — When paired together, the effects became more pronounced. Both deep and REM sleep were significantly reduced, and participants spent about 15 additional minutes awake during the night. Notably, this increase in wakefulness did not occur with aircraft noise alone or pink noise alone.
So, Should You Ditch Your Sound Machine?
These study findings are vital, as many people today use broadband noise not just for sleep, but also as a relaxation tool throughout the day. Case in point: White noise and ambient podcasts now total about 3 million listening hours per day on Spotify. Meanwhile, the top five “white noise” videos on YouTube have collectively been viewed more than 700 million times.6 Even so, research on how broadband noise affects sleep remains limited and inconclusive.
• Consistent REM disruptions are more damaging than you think — People whose REM sleep is always disrupted have a higher risk of developing mental health issues like depression and anxiety and even Parkinson’s disease. What’s more, majority of people today, particularly adults, are sleep deprived. This means that every minute of REM sleep matters.
• Use sound machine as a tool, not a mandate — If sound machines work for you, then use them in a smart and strategic manner. Basner recommends playing it at a low volume and setting a timer instead of letting it play through the night. “I don’t want to discount that there may be something behind it, because so many people are using it,” he added.7
• Wearing earplugs is a better way to improve sleep quality — This is a simpler — and more cost-friendly — strategy to shut off disruptive noise at night. Around 16% of Americans wear earplugs during bedtime to get the restful sleep they need.8
In the featured study, earplugs restored about 72% of the deep sleep that environmental noise had taken away. That’s equivalent to nearly 17 minutes of N3 deep sleep restored. In nearly every measurement, including sleep stages, awakenings, sleep depth, and morning mood, sleeping with earplugs looked far more similar to sleep during the quiet control night than to any noise-exposed condition.
• Earplugs performed well even during repeated noise events throughout the night — Only at the loudest level tested, 65 dB (which is similar to a noisy vacuum cleaner or busy street heard from indoors), did the protective effect begin to weaken.
• Participants also found earplugs comfortable — Even though the researchers used ordinary foam earplugs for this test, the participants still reported that they slept better with them. This is notable, since comfort and usability often limit whether people stick with sleep tools long-term.
“It is likely that both comfort and sound attenuation could be further improved by using high-fidelity or even custom-fit earplugs instead, although this would have to be shown,” the researchers added.9
Are Sound Machines Safe for Babies and Kids?
During the first weeks of life, newborns spend the majority of their time sleeping — In fact, newborns are recommended to get around 14 to 17 hours of sleep per day, according to the National Sleep Foundation (NSF). This means that these young children spend significantly more time in REM sleep than adults.
• Many parents place sound machines beside their newborns’ or toddlers’ beds — They do this with the best of intentions, to help their children fall asleep and stay asleep through the night. However, based on the featured research, this habit could be doing more damage, as they are more susceptible to the possible harms of pink noise exposure.
• REM sleep loss may be more pronounced in young children — Although the study did not observe the effects of broadband noise on these age groups, the researchers still warn parents to be careful in using sound machines until there’s more conclusive research on their effects on younger brains.
“Overall, our results caution against the use of broadband noise, especially for newborns and toddlers, and indicate that we need more research in vulnerable populations, on long-term use, on the different colors of broadband noise, and on safe broadband noise levels in relation to sleep,” Basner said.10
• The volume level of the machine is also a concern — Excessively high volumes can pose risks over time. One study published in the National Library of Medicine reported that white noise played above recommended limits may negatively affect young children’s hearing and language development.11
For context, the safe noise level for hospital nurseries is around 50 decibels (dB). For adults, white noise is typically regarded as safe between 50 and 70 dB. Beyond that range, hearing protection may be necessary to reduce the risk of long-term damage.12
To summarize, below is a comparison of the different types of broadband noises made by sound machines and the recommendations based on the research findings.
| Noise type | Sound profile | Effect on sleep | Recommendation |
|---|---|---|---|
| Pink noise | Softer, deeper static (like steady rainfall or rushing water) | Reduced REM sleep by ~19 minutes per night in lab settings | Use cautiously, especially for children whose brains need more REM sleep |
| White noise | Even static across all frequencies (like TV static or a fan) | Masks disruptive sounds but shows no clear benefit for sleep quality | Keep volume low (50 to 70 dB), use a timer, place device 3+ feet away |
| Brown noise | Deep, rumbling static (like thunder or strong wind) | Limited research available; effects on sleep architecture unclear | Apply same safety precautions as pink/white noise until more data exists |
How to Use a Sound Machine Safely
If you’re not ready to give up your sound machine entirely, you can still minimize the risks. Here’s a practical, research-aligned setup guide you can implement tonight:
1. Use the lowest effective volume — Set your sound machine to the minimum level that still masks your specific trigger noises, like traffic or snoring. Lower loudness means less risk of disrupted sleep over time. Aim for 50 dB or below — roughly the volume of light rainfall.
2. Increase the distance from your bed — Place the device across the room, not on your nightstand. Sound pressure decreases with distance, so moving your machine even 3 to 6 feet farther from your ears significantly reduces exposure while still providing masking benefits.
3. Set a sleep timer or auto-off feature — You don’t need broadband noise running all night. Set a timer for 30 to 60 minutes — enough time to fall asleep. Once you’re in deep sleep, your brain is less sensitive to moderate environmental sounds anyway.
4. Consider earplugs as an alternative — In the featured study, simple foam earplugs restored about 72% of the deep sleep lost to environmental noise, outperforming pink noise in nearly every measurement. Try them instead of, or alongside, your sound machine.
5. Combine with physical noise control — Address noise at the source: heavy curtains, door sweeps, draft stoppers, and soft furnishings all reduce sound transmission. These passive solutions don’t carry the REM-disruption risks of continuous broadband noise.
6. Run a one-week self-experiment — If you wake up groggy despite “sleeping” seven to eight hours, try removing your sound machine for one week. Track your morning alertness, mood, and energy. If you feel more restored without it, that’s your answer.
Frequently Asked Questions (FAQs) About Sound Machines and Sleep
Q: Can pink noise disrupt rapid eye movement (REM) sleep?
A: Yes, recent controlled sleep-lab research suggests pink noise may reduce REM sleep, which is the stage associated with dreaming, memory consolidation, emotional regulation, and brain development. In laboratory conditions, participants exposed to pink noise experienced a measurable reduction in REM sleep compared to quiet conditions.
While pink noise is often marketed as calming, continuous broadband sound may act as an ongoing auditory stimulus that subtly interferes with the brain’s natural sleep cycling. The effect may be especially relevant for people already struggling with sleep quality or those who rely on noise all night at moderate volumes.
Q: What is a safe decibel level for sleep?
A: For most adults, sleep experts generally recommend keeping nighttime sound exposure around 50 decibels (dB) or lower — roughly the sound of light rainfall. Some guidance considers 50 to 70 dB acceptable for adults, but lower is better when possible. For infants and young children, caution is even more important, and volume should remain at or below nursery safety standards (around 50 dB).
Q: Are sound machines safe for babies?
A: Parents should use caution. Babies spend significantly more time in REM sleep than adults, and REM plays a critical role in brain development. Emerging research suggesting that certain types of broadband noise may reduce REM sleep raises questions about prolonged overnight use in infants and toddlers. Additionally, excessive volume may pose hearing risks over time.
Environmental fixes — such as blackout curtains, soft furnishings and white-noise alternatives at low levels — may be safer first-line options.
Q: Where should I place a sound machine in the bedroom?
A: Placement significantly affects sound exposure. For safer use, position the device across the room, not on your nightstand. Keep it at least 3 to 6 feet away from your bed or your child’s crib. Use the lowest volume that masks your triggers, and never direct the speaker toward your ears. Sound intensity drops as distance increases, so moving the machine farther away reduces the decibel level reaching your ears while still providing masking benefits.
Q: Do I need a timer or should a sound machine run all night?
A: For many people, running a sound machine all night is unnecessary. Once you fall asleep — especially after entering deeper sleep stages — your brain becomes less sensitive to moderate background sounds. Using a 30- to 60-minute timer may reduce potential REM disruption and limit prolonged noise exposure. Continuous overnight use may not provide added benefit and could increase the risk of sleep-stage interference.
Q: What’s the difference between pink, white and brown noise?
A: The “color” of noise refers to how sound frequencies are distributed:
• White noise — Equal intensity across all audible frequencies; sounds like steady static or a fan.
• Pink noise — Emphasizes lower frequencies; softer and deeper, often compared to rainfall or rushing water.
• Brown noise — Even more weighted toward low frequencies; deeper, rumbling sound similar to thunder.
Pink noise has recently drawn attention due to findings suggesting it may reduce REM sleep in certain lab settings. White and brown noise are widely used for sound masking, but high-quality evidence comparing long-term effects on sleep architecture remains limited.
Q: Are there alternatives to sound machines that are safer?
A: Yes. Depending on the source of nighttime noise, alternatives may better preserve sleep quality:
• Earplugs — In laboratory studies, earplugs protected deep sleep more effectively than pink noise during aircraft noise exposure.
• Physical soundproofing — Door sweeps, draft stoppers, heavy curtains and rugs can reduce environmental noise without continuous auditory stimulation.
• Fans or air purifiers at a distance — Provide gentle masking without placing a speaker near your head.
• Behavioral sleep strategies — Consistent bedtime, light control and stress reduction may reduce the perceived need for artificial noise.
If you wake feeling groggy despite adequate sleep duration, consider a one-week trial without broadband noise to assess how your body responds.
