Pink noise vs brown noise
How they sound, how their spectra differ, and which suits sleep or focus.
Last updated: (originally published )
Hear both side by side
Play pink and brown noise in your browser with a sleep timer. Nothing is recorded or uploaded.
Open the noise generatorWritten by Nayeem, Software Developer of SoundLevelTest.com · Latest update: Added an 'Is rain white noise?' answer section and FAQ explaining why rain sounds closer to pink or brown noise. First published with a spectral slope table, side-by-side comparison, sleep and focus research summary and an original spectrum chart.
What is the difference between pink and brown noise?
Pink noise drops 3 dB in power per octave, so every octave carries equal energy and it sounds like steady rain. Brown noise drops 6 dB per octave, so high frequencies fade further and it sounds like a deep rumble. Pink has more sleep research; brown is popular for focus.
Spectrum compared, relative to 1 kHz
Power per hertz in dB. Positive numbers mean more energy than at 1 kHz.
| Frequency | White | Pink | Brown |
|---|---|---|---|
| 63 Hz | 0 dB | +12 dB | +24 dB |
| 125 Hz | 0 dB | +9 dB | +18 dB |
| 250 Hz | 0 dB | +6 dB | +12 dB |
| 500 Hz | 0 dB | +3 dB | +6 dB |
| 1 kHz | 0 dB | 0 dB | 0 dB |
| 2 kHz | 0 dB | -3 dB | -6 dB |
| 4 kHz | 0 dB | -6 dB | -12 dB |
| 8 kHz | 0 dB | -9 dB | -18 dB |
Side by side
| Colour | Slope | Sounds like | Common use |
|---|---|---|---|
| White noise | 0 dB/octave | Bright hiss, like TV static | Masking speech and office chatter |
| Pink noise | -3 dB/octave | Balanced, like steady rain | Sleep and general relaxation |
| Brown noise | -6 dB/octave | Deep rumble, like a waterfall | Focus and low-frequency masking |
Sleep and focus: what the research shows
Pink noise has the most direct sleep evidence. Zhou et al. (2012, Journal of Theoretical Biology) reported more stable sleep with steady pink noise, and Papalambros et al. (2017, Frontiers in Human Neuroscience) found pink noise bursts timed to slow waves improved deep sleep and next-day recall in older adults. Both studies were small. Brown noise is widely recommended online for focus, but there is little controlled research on it yet. The honest answer is to try both at a low level and keep the one you find easier to ignore.
Is rain white noise?
Not in the strict sense. People call rain “white noise” because it is steady and masks other sounds, but true white noise has equal power at every frequency and sounds like harsh hiss. Rain sounds softer because its high frequencies are weaker, which puts most rain closer to pink noise.
Is rain white, pink or brown noise?
Real rain is not a perfect colour of noise. Its spectrum depends on drop size, how hard it falls and what it hits: a tin roof, leaves, a window or a pavement. Light, steady rain on a roof is usually described as pink-like, with balanced energy per octave. Heavy downpours and distant thunder add low-frequency rumble, which moves the sound toward brown noise. Close splashes on hard surfaces add crisp highs, which is the part that sounds most like white noise.
Hear the difference yourself
Play white, pink and brown noise one after another in the white noise generator. Most listeners find pink closest to a rain shower and brown closest to a heavy storm. If you use rain sounds for sleep, the same low-volume advice below applies.
Keep the volume low
Steady noise played all night adds to your daily sound dose. Aim for roughly 40 to 50 dB at the pillow, and keep infant sound machines well away from the crib at the lowest useful setting (Hugh et al., 2014, Pediatrics). Measure it with the sound level meter, and see how levels compare on the decibel chart. Snoring partner? See how loud snoring gets.
General information, not medical advice. Talk to a doctor about ongoing sleep or attention problems.
Questions people ask
What is the difference between pink noise and brown noise?
Both are random noise with more energy in low frequencies than white noise. Pink noise loses 3 dB of power per octave, so it sounds balanced, like steady rain. Brown noise loses 6 dB per octave, so treble is much weaker and it sounds like a deep rumble or a distant waterfall.
Is pink or brown noise better for sleep?
Most published sleep studies used pink noise, for example Zhou et al. (2012) and Papalambros et al. (2017), and found small improvements in sleep stability or deep sleep in small groups. Brown noise has little direct sleep research. Pick whichever you find more comfortable at a low volume.
Is brown noise better for focus or ADHD?
Many people report that brown noise helps them concentrate, but controlled studies on brown noise specifically are scarce. Some research on white and pink noise in people with ADHD shows small benefits. Treat it as a personal preference, not a treatment.
Why is it called brown noise?
It is named after Robert Brown and Brownian motion, not the colour. The signal is a random walk, which produces the 1/f² spectrum. It is also called red noise.
Why is it called pink noise?
By analogy with light: shifting white light's energy toward longer, lower-frequency wavelengths looks pinkish. Pink noise has equal energy in every octave, which is why audio engineers use it to tune speakers.
How loud should sleep noise be?
Keep it quiet. For adults, a level you can easily talk over, roughly 40 to 50 dB at the pillow, is a sensible ceiling. For babies, Hugh et al. (2014, Pediatrics) found some sound machines exceed 85 dBA at 30 cm, and advised placing them far from the crib at low volume. Check with a sound meter.
Is rain considered white noise?
Not technically. White noise has equal power at every frequency and sounds like hiss. Rain has weaker high frequencies, so light steady rain sounds closer to pink noise, and heavy rain with thunder leans toward brown noise. It is often called white noise only because it is steady and masks other sounds.
Can I hear pink and brown noise for free?
Yes. The white noise generator on this site plays white, pink and brown noise in your browser with a sleep timer, and no audio is uploaded.