Most people pick a sleep sound the same way they pick a pillow. Try a few, find one that doesn't annoy you, stick with it. White noise sounds like a fan. Brown noise sounds like a river. Pink noise sounds, well, somewhere in between. But over the last decade, a quiet pile of sleep lab research has been building around one specific finding: pink noise, played the right way during deep sleep, can actually improve what your brain remembers the next day.
That's not a wellness influencer claim. It's measurable on memory tests, in a sleep lab, with EEG sensors on people's heads. It also has limits that matter a lot for anyone hoping to get the same effect from an app. If you've been reading up on the differences between brown, white, and pink noise, this is the next layer of the story.
What is pink noise?
Pink noise is a frequency distribution where energy decreases as frequency rises, at roughly 3 dB per octave. In practice the low notes are louder than the high notes, but the drop-off is gentler than brown noise. White noise, by contrast, spreads equal energy across every frequency, which is why it sounds hissy and bright.
Pink noise sounds like steady rainfall on leaves, or a distant waterfall. Many natural sounds have a roughly similar spectrum.
Pink noise is also the sound researchers have most often used in studies that play brief bursts of sound during deep, slow-wave sleep, to see whether sound could nudge those slow brain rhythms in a useful direction.
Does pink noise improve memory?
Pink noise can improve next-day memory under sleep lab conditions, but the effect depends on timing. In a 2017 Northwestern University study of adults aged 60 to 84, short pink noise bursts timed to slow brain waves during deep sleep led to a larger overnight gain in word-pair recall. Continuous pink noise from an app has not shown the same benefit, and one 2023 study suggests it may even interfere.
In 2017, a Northwestern University team (Papalambros and colleagues, with Dr. Phyllis Zee as senior author) published a widely cited study in Frontiers in Human Neuroscience. They had 13 older adults (60 to 84 years old) come into a sleep lab for two nights. On one night, the researchers played short bursts of pink noise timed precisely to the up-phase of each participant's slow brain waves while they were in deep sleep. On the other night, the same setup was used but with no sound played. Participants did word-pair memory tests in the evening before sleep and again the next morning.
The result was striking. Recall improved overnight by about 9 words on average after the stimulation night, versus about 3 words after the sham night, so the overnight gain was roughly three times larger (about 27% versus 6%). Slow-wave activity, the kind of brain activity tied to memory consolidation, was higher while the pulses were playing, though across the whole night it was similar on both nights. And the people whose slow waves rose most during stimulation also showed the biggest jump in memory.
This wasn't just a comfort thing. Participants did not report sleeping better, feeling more alert, or being in a better mood after the stimulation night. The timed sound appeared to strengthen the brain rhythms that sleep science has long associated with locking memories into long-term storage.
In a small group of older adults, short pink noise pulses timed to slow-wave sleep boosted slow-wave activity while they played and were followed by a larger overnight gain in word recall.
Why timing matters more than volume
Here's the catch, and it's a big one. The Northwestern study used a technique called closed-loop acoustic stimulation. EEG sensors measured each participant's brain waves in real time, and a computer triggered short pink-noise bursts timed to the rising phase of each slow wave, with the sound switching on and off in blocks. Timing is the whole point: in an earlier 2013 study in Neuron (Ngo and colleagues, University of Tübingen), sound pulses in phase with slow oscillations improved word-pair memory in young adults, while pulses out of phase did not.
You can't replicate that at home, not with a consumer app, and especially not with a Bluetooth speaker on your nightstand. Steady pink noise played all night has much less behind it. In a 2023 study in Frontiers in Human Neuroscience (Vickrey and Lerner), 72 people slept with all-night pink noise, slept in silence, or stayed awake, and the pink noise group gained no more insight into a hidden pattern than the silent sleep group. Pink noise also cut short their first stretch of light N1 sleep, which predicted insight, so the authors suggest it may interfere rather than help.
So why does that matter for you, lying in bed tonight, with no EEG headset and no lab tech? Because it changes what you should expect, and how you should use it. Pink noise played all night isn't going to reproduce the lab result. What it can still do is narrower.
What continuous pink noise still seems to do
Continuous pink noise, without the precise timing used in lab studies, has mixed results. One older study found more stable sleep, a recent one found less REM sleep, and the case for noise as a sleep aid in general is rated very low quality. Its most dependable use is masking environmental noise, and it needs no equipment beyond a speaker.
- Possibly more stable sleep. A 2012 study in the Journal of Theoretical Biology (Zhou and colleagues) found a higher percentage of stable sleep time with steady pink noise in 40 overnight sleepers and 10 nappers, measured from heart signals rather than brain waves.
- Possibly less REM sleep. A 2026 sleep lab study in Sleep (Basner and colleagues, University of Pennsylvania) found that pink noise at 50 dB reduced REM sleep compared with quiet nights.
- Less disruption from environmental noise, the classic masking effect, though a 2021 systematic review in Sleep Medicine Reviews (Riedy and colleagues) rated the evidence for continuous noise as a sleep aid as very low quality.
It's not the three-times-larger overnight memory gain from the lab. Steady pink noise is best treated as a comfortable masking sound, not a memory or deep sleep treatment. For people whose sleep is broken up by outside noise, masking alone can be worth having.
Pink noise vs the other colors, for memory specifically
White noise gets the most attention because it's the most aggressive masker. If your neighbor's dog barks at 2 AM, white noise covers it best, though some people find the high-frequency hiss harsh. Brown noise is gentler on the ears and feels deeper, but it does little to mask high-pitched sounds.
Pink noise sits in between: enough mid-range energy to mask common noises, and softer than white noise. It is also the color used in the timed-pulse memory studies. But no study has shown that playing any noise color steadily through the night improves memory, so for steady playback pick the color you find most comfortable.
This doesn't mean you should never use white or brown noise. If you've trained your brain on white noise for years, switching cold-turkey usually doesn't go well. The body's relationship with sleep sounds is more about consistency than chasing the most "scientific" option each week.
How do you use pink noise for sleep?
To use pink noise for sleep, keep the volume moderate, at the lower end of the 50 to 70 dB range in our volume guide. Start playback while you are winding down, so the sound becomes a sleep cue. Use a sleep timer if you don't need masking all night, use a clean source, and layer other sounds sparingly.
Keep the volume moderate. In the Northwestern study, participants set the pulses between 30 and 50 dB, a level they said would not disturb them. For steady all-night noise, our guide to how loud white noise should be suggests 50 to 70 dB at the pillow, with 70 as the ceiling. Given the Penn finding on REM at 50 dB, staying near the bottom of that range is sensible. If the noise is louder than someone talking to you at a relaxed volume, it's too loud.
Start before sleep, not after. Begin playback while you're still winding down, not the moment your head hits the pillow. The familiar sound becomes a sleep cue your nervous system learns over weeks. Pair it with a consistent bedtime, and you're stacking a behavioral signal on top of a physiological one.
Decide between all night and a timer. Masking only works while the sound plays, so if outside noise wakes you later in the night, you may want it running. If you mainly need help falling asleep, a sleep timer that fades out limits how much of the night you spend under noise, which the REM finding above makes worth considering.
Use a clean source. Many "pink noise" tracks on YouTube and free apps are heavily compressed or layered with other sounds, which mangles the spectral pattern you chose pink noise for. The sound needs to be a true pink-spectrum signal, not a generic ambient track labeled "pink noise" for SEO.
Layer carefully if you layer at all. Pink noise on its own is the cleanest version. Adding rain or ocean sounds is fine for comfort, but every layer changes the overall spectrum a little. Since steady noise has not been shown to help memory either way, choose the mix you find most comfortable.
Where IOn Sleep fits in
This is one of the reasons we built IOn Sleep the way we did. The pink, white, and brown noise tracks are stored as lossless FLAC with seamless crossfade looping, with no backing music layered on top. You can play them on their own or mix up to 3 sounds with independent volume control.
IOn Sleep also includes delta, theta, and alpha binaural beat modes for people interested in brainwave entrainment alongside sound masking, plus the IOn Flow program that steps through alpha, theta, and delta over the session. The whole thing works offline with no account, sleep tracking data stays on your device, and Premium is ad-free. The point is to give your brain a clean signal and then get out of the way.
If you're new to sleep sounds entirely, pink noise is a gentle starting point. Many light sleepers find it easier to tolerate than white noise, and it is the color most often used in slow-wave sleep research, though that research used timed pulses. Try it for two weeks at a consistent volume and bedtime. The first few nights might feel underwhelming if you've been using something more aggressive. After a week or two, many people stop noticing the sound.
The bottom line
Pink noise isn't a magic memory pill. The dramatic Northwestern result depended on precise closed-loop timing that no consumer app can deliver yet. Continuous pink noise is a reasonable masking sound with mixed evidence beyond that: one study found more stable sleep, another found less REM sleep, and another found no help with insight. For students, shift workers, people in cognitively demanding jobs, or anyone over fifty noticing changes in recall, it's a low-cost thing to try at a moderate volume, but not a memory treatment. If memory changes worry you, raise them with a doctor.
Pair it with the basics. Consistent sleep schedule, dark room, cool temperature, and a wind-down routine that doesn't end with doomscrolling. The audio is the easy part. The rest of sleep hygiene is where most of the actual gain lives. Pink noise is a pleasant tool you can layer on top of a solid foundation, and the research on timed sound during sleep is worth watching as it develops.
This post is part of our sleep guides.