What actually differs between them?
The two names describe how loudness is spread across frequency, not how loud the sound is. The Sleep Foundation defines white noise as a noise containing all frequencies across the spectrum of audible sound in equal measure, which is why it is also called broadband noise and why people compare it to the static from an untuned radio or television. Pink noise steps the volume of each octave down by about 3 decibels. Brown noise steps down roughly twice as steeply as pink, which is why the Cleveland Clinic describes it as having the highest emphasis on lower frequencies and a bass-heavy, deep rumbling quality. Same raw ingredient, different tilt. Play them back to back at matched volume and the tilt is the only thing you hear.
Does either one help you sleep?
Less than the internet suggests. A 2021 systematic review in Sleep Medicine Reviews screened articles from three databases and assessed 38 of them, covering sleep onset latency, fragmentation, quality and duration. The authors found so much variation that the extremes of the literature were that continuous noise improves sleep and that continuous noise disrupts it. Rated against the GRADE criteria, the quality of evidence for continuous noise improving sleep came out very low, which the authors note contradicts its widespread use, and they called for more research before continuous noise is promoted as a sleep aid. The Cleveland Clinic reads the same 2020 review the same way: limited evidence, with some studies showing delayed or disrupted sleep.
Which one do people reach for to focus?
Brown noise, mostly, and the claims have outrun the research. The Cleveland Clinic lists the popular claims plainly, focus, ADHD symptoms, sleep and tinnitus, and then quotes a psychiatrist saying the benefits are still under research, that the research is minimal, and that there are no significant studies comparing brown noise to white or pink noise for ADHD. The nearest thing to a measured result involves white noise, not brown. A 2014 study of 90 school children aged 8 to 10 found moderate white noise improved executive-function performance in the least attentive group and worsened performance in the most attentive group. That is a real finding, and it is also a finding that cuts both ways depending on who is listening.
How loud, and for how long?
This is the part worth getting right, because it is the part with settled numbers behind it. The National Institute on Deafness and Other Communication Disorders states that sounds at or below 70 A-weighted decibels are unlikely to cause hearing loss even after long exposure, and that long or repeated exposure to sounds at or above 85 dBA can cause hearing loss. The louder the sound, the less time it takes. The Cleveland Clinic's advice is more conservative still: listen in brief periods of 10 to 15 minutes at lower volumes, and if you are listening at bedtime, use a timer so your ears get a break before you fall asleep. A timer costs nothing and removes the question entirely.
In short
- White noise spreads power evenly across frequencies; brown noise concentrates it at the low end.
- A 2021 review of 38 studies rated the evidence for continuous noise improving sleep as very low quality.
- No published study compares brown noise to white or pink noise for ADHD, per the Cleveland Clinic.
- Sounds at or below 70 dBA are unlikely to harm hearing; 85 dBA and above can, with long or repeated exposure.
- Since the evidence does not pick a winner, your own preference is a reasonable way to choose.
Related guides
- Noise colors explained (white, pink, brown): Noise colors describe how a sound's energy is distributed across frequency.
- Brown noise: Brown noise is broadband sound weighted heavily toward low frequencies, so it comes across as a deep rumble rather than a hiss.
- Pink noise vs white noise: White noise holds every audible frequency at equal power, so it sounds higher-pitched, like a humming air conditioner.