Brown noise and red noise are the same sound. That surprises most people. The bigger surprise is what recent research shows about colored noise and sleep: it can help in a noisy room, but it is not a free upgrade for everyone, and louder is not better.

This article explains how these sounds differ, what the latest studies show, and how to use them safely if you choose to.

What Does “Color” Mean in Noise?

Every sound is made of frequencies. Low frequencies sound deep, like a rumble. High frequencies sound sharp, like a hiss.

A “noise color” describes how much energy a sound has at each frequency. The name borrows from light. White light contains all visible colors at once, and white noise contains all audible frequencies at once.

The three most common sleep sounds sit on a scale from bright to deep:

• White noise is the brightest.
• Pink noise sits in the middle.
• Brown (red) noise is the deepest.

Pink noise is not in the title, but it matters here. It sits between white and brown, and it is the color with the most recent sleep research.

White Noise

White noise has equal energy across every frequency. Because your ear is more sensitive to higher pitches, white noise sounds like a hiss or radio static.

Everyday examples:

• An untuned radio or TV
• A hissing air vent
• Many basic sound machines

Some people find it soothing. Others find it harsh, especially at higher volumes.

Pink Noise

Pink noise lowers the energy as the pitch rises. The result sounds softer and more balanced than white noise.

Everyday examples:

• Steady rain
• Wind through trees
• Waves on a beach

Brown Noise and Red Noise

Brown noise lowers the high frequencies even more than pink noise. It sounds like a deep, steady rumble.

Everyday examples:

• A distant waterfall
• Heavy surf heard from indoors
• The low roar inside an airplane cabin

The name has nothing to do with the color brown. It comes from Brownian motion, the random movement of tiny particles first described by the botanist Robert Brown. “Red noise” is simply another name for the same sound, chosen to match the light analogy, since red is the deepest end of the visible spectrum.

So if your app offers both “brown” and “red,” they should sound nearly identical. Some apps tweak the settings slightly, but in acoustics the terms mean the same thing.

Quick Comparison

Feature	White noise	Pink noise	Brown / red noise
Sound	Bright hiss, static	Softer, like steady rain	Deep rumble, like a waterfall
Energy at high pitches	Highest	Medium	Lowest
Common complaint	Can feel harsh	Few	Can feel “muffled” to some
Sleep research	Most studies overall	Most rigorous recent lab trial	Very little direct research

What the Research Shows

The studies below are from the last five years. Randomized controlled trials (RCTs) and reviews of RCTs carry the most weight, so they come first.

Evidence summary

Question	Best available evidence	Strength
Does white noise improve reported sleep quality?	Meta-analysis of RCTs (2025)	Moderate, with quality limits
Does pink noise change sleep stages in healthy adults?	Randomized crossover lab trial with sleep studies (2026)	Moderate, small sample
Does sound help hospital patients sleep?	Systematic review of 7 RCTs (2025)	Moderate
Is brown/red noise better than white or pink for sleep?	No sleep trials. One small lab study on arousal (2025, not yet peer reviewed)	Low

White noise: helpful for reported sleep quality

The largest recent analysis pooled randomized trials of white noise in infants, adults, and older adults. Adults who used white noise improved their sleep quality scores by about 3.7 points on the Pittsburgh Sleep Quality Index, a 21-point questionnaire where lower is better. Older adults improved by about 2.7 points. These are meaningful changes.

The authors were clear about the limits. The studies varied a lot in design and quality. Most measured how people felt about their sleep, not what their brain was doing during sleep.

A separate review of 34 studies on white and pink noise reached a similar view. Many studies showed some benefit, but the authors found no strong evidence overall. On the positive side, none of the short-term studies reported harm.

Hospitals and noisy places: where sound helps most

Sound works best when it has something to cover. A 2025 Mayo Clinic systematic review looked at seven randomized trials with 496 hospitalized adults. White noise and similar masking sounds improved sleep efficiency, meaning more of the time in bed was spent asleep. Patients tolerated it well.

One ICU trial is worth noting because it tested all three colors. Patients used an app that played white noise on day one, pink noise on day two, and brown noise on day three. Sleep quality was better than in the control group on all three days. The ICU noise level was above 60 decibels, which is very loud for sleep. The study was small and relied on patient ratings, but it suggests the color mattered less than the masking.

Pink noise: an important caution

The most rigorous recent study comes from the University of Pennsylvania, published in the journal Sleep in 2026. Twenty-five healthy adults spent seven nights in a sleep lab. Researchers recorded brain waves through a full overnight sleep study.

What they found:

• Traffic and aircraft noise cut deep sleep.
• Pink noise played alone at 50 decibels, about the level of moderate rain, cut REM sleep by nearly 19 minutes per night.
• Pink noise played over traffic noise made sleep worse, not better. Both deep sleep and REM sleep dropped, and people spent about 15 more minutes awake.
• People also reported lighter, poorer sleep on pink noise nights.
• Simple foam earplugs protected sleep from traffic noise far better. They only started to fail at the loudest level tested.

REM sleep supports memory, mood, and emotional balance. Young children spend much more of their sleep in REM, which is why the researchers urged extra caution for kids.

This was one study in healthy adults with no sleep complaints, over a short period. It does not prove that pink noise harms everyone. But it is the strongest objective data available, and it challenges the idea that colored noise is automatically good for sleep.

Brown and red noise: popular, but barely studied

Brown noise has a large following online. Direct sleep research on it is almost nonexistent.

A small 2025 lab study tested whether white, pink, and brown noise affect the body’s arousal level differently. Researchers measured pupil size, a reliable marker of how alert the nervous system is. They found no difference between the three colors. This study has not yet completed peer review, so treat it as early data.

What this means for you: brown noise may feel more pleasant, and comfort matters for sleep. But there is no evidence that brown noise deepens sleep more than white or pink noise does.

A note on “pink noise for deep sleep” headlines

You may have read that pink noise improves deep sleep and memory. Those studies usually tested something different. They used short bursts of pink noise timed precisely to brain waves during deep sleep, using lab equipment that reads the brain in real time.

A 2022 meta-analysis found this timed approach helped memory in adults under 35, but not in older adults, and did not change overall sleep structure. A 2023 meta-analysis found the memory benefit was smaller than early studies suggested. A pink noise track playing all night from your phone is not the same thing.

So Which Color Is Best?

Based on current evidence:

• No color is proven better than another for sleep. The benefit, when there is one, comes from masking disruptive sounds.
• Sound helps most in noisy places. Think city traffic, a snoring partner, thin apartment walls, or a hospital room.
• In a quiet room, added noise may do more harm than good. The 2026 lab study suggests continuous sound can trim REM sleep.
• Pick the color you find most comfortable. Many people prefer pink or brown because white noise can sound sharp.

Who May Benefit, and Who Should Be Careful

Sound masking may help if you:

• Live near a busy road, rail line, or airport
• Share a bed or wall with someone who snores
• Work night shifts and sleep during the day
• Sleep in a hospital or other loud setting

Be more careful if you:

• Already sleep in a quiet room
• Have tinnitus or hearing concerns (talk with your doctor first)
• Are using sound for a baby or young child

A Special Note for Parents

A 2024 review in the journal Sleep Medicine found that some infant sound machines can exceed 91 decibels at maximum volume. That is louder than workplace safety limits allow for a two-hour adult shift. Animal studies link loud, continuous noise to delayed hearing development. Low-volume sound during sleep may still be helpful.

If you use a sound machine for your child:

• Keep the volume low, around the level of a quiet conversation or softer.
• Place it across the room, not on or next to the crib.
• Use it for sleep only, not as all-day background noise.

How to Use Sleep Sounds Safely

If you want to try white, pink, or brown noise, these steps keep the benefit and lower the risk:

1. Fix the noise source first. Use earplugs, heavy curtains, or a fan, or move your bed away from the street-facing wall. Earplugs outperformed pink noise in the 2026 study.
2. Use the lowest volume that works. Aim for below 50 decibels at your pillow. A free decibel meter app can check this.
3. Keep the speaker away from your head. Place it across the room, not under your pillow.
4. Try a timer. If your main problem is falling asleep, a 30 to 60 minute timer gives you the help without sound all night.
5. Choose the color you like. Comfort matters more than the color name.
6. Test it for two weeks. Track how rested you feel. If you feel worse, stop and see if things improve.
7. See a sleep specialist if problems continue. Ongoing trouble falling or staying asleep may point to insomnia, sleep apnea, or another treatable condition. Sound machines do not treat these.

The Bottom Line

• Brown noise and red noise are the same sound.
• White, pink, and brown noise differ in pitch, not in proven sleep benefits.
• Sound masking can help in noisy environments, especially hospitals and city bedrooms.
• The strongest recent lab study found pink noise reduced REM sleep in healthy adults, and earplugs worked better against outside noise.
• Keep the volume low, especially for children.
• If sleep problems last more than a few weeks, a sleep evaluation will help more than any sound.

Disclaimer

This article is for general educational purposes only and does not replace personal medical advice. Talk with your doctor or a board-certified sleep medicine physician before making changes to your sleep routine, especially if you have a sleep disorder, hearing condition, or concerns about a child’s sleep.

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References

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