• 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

• 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

• 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

• 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

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.