Why is brown noise often recommended for ADHD focus?

The bass-heavy spectrum gives the auditory cortex a steady non-stimulating floor that masks intrusions without itself becoming an attention magnet. White's high-frequency content tends to keep high-freq-sensitive circuits more activated; brown lets them relax. Individual results vary.

What does the sleep timer do?

Counts down 15/30/60 min from when audio actually starts playing — arming while idle then pressing Play resets the countdown. Audio fades over the last 4 seconds. Closing the tab cancels it.

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Brown Noise Generator

Free, browser-only brown (or red) noise generator using a leaky-integrator filter for −6 dB / octave power roll-off — deeper and rumblier than white or pink. Live log-frequency spectrum with a static −6 dB/oct slope reference, real-time measured slope readout, A/B/C color comparison across white / pink / brown, sleep timer (15 / 30 / 60 min), and WAV download. Commonly used for ADHD focus, deep relaxation, sleep, and audio testing in the low-frequency bands.

Playback

Volume 30 %

Brown noise's low-frequency emphasis can drive sub-bass speakers hard at high levels. Start moderate.

Idle — press Play.

Live measurements

Current color

—

white / pink / brown

Sample rate

—

AudioContext.sampleRate

Measured slope

—

least-squares dB/oct — brown ≈ −6

Average level

—

mean dB across all bars

Sleep timer

Time remaining

—:——

Audio fades over the last 4 seconds so you aren't jolted by an abrupt cutoff.

Download WAV

Length

10 s 30 s 60 s

16-bit PCM mono brown noise (leaky integrator, gain 2.0) at the audio context's sample rate. 60 s briefly freezes the UI (~250 ms) while filling the buffer.

Generated locally — never uploaded.

Live FFT spectrum — 48 bars, log frequency (20 Hz → Nyquist) · cyan dash = ideal −6 dB/oct

Brown Noise — What It Is and Where to Use It

Brown noise — also called red noise — is a random signal whose power falls off at −6 dB per octave, or equivalently as 1/f². That's twice the per-octave roll-off of pink (−3 dB/oct) and an enormous shift from white (flat per Hz). To the ear, brown is the deepest, rumbliest, most ocean-like of the standard noise colours. The bulk of its energy sits in the bass and sub-bass region.

The name “brown”

Despite the colour analogy with white and pink, brown noise isn't named for a colour at all — it's named after Robert Brown, the 19th-century botanist who described the random walk of pollen particles in water. Mathematically, brown noise is generated by integrating a white-noise process — the same operation that turns instantaneous random impulses into Brownian motion. The integration step is what produces the 1/f² spectral slope.

How this generator works

White noise is fed through a leaky integrator: each output sample is a small weighted addition of the latest white sample to a slowly-decaying memory of past samples (output = (last + 0.02 · white) · 0.997). The decay term keeps the signal bounded; the integration is what carves the −6 dB/oct slope. The output is multiplied by 2.0 and clamped to ±1 for the buffer — the clamp fires on roughly 0.04% of samples (verified in Node), well below the threshold where clipping would distort the spectral character.

Reading the spectrum

The plot above uses a log-frequency X axis. Brown noise's per-bin power drops at −6 dB / octave, so the bars slope steeply downward from left to right — visibly twice as steep as the same plot would show for pink noise. The dashed cyan line is the textbook −6 dB/oct reference, auto-anchored on the first frame of valid spectrum data so it visually sits on top of the live bars at 1 kHz; if the bars track that line across the X range you have a clean brown signal. The Measured slope readout fits a least-squares line through the bars in real time and reports the actual dB/oct slope — expect convergence to about −6.0 within a few frames.

Common uses

ADHD focus and deep concentration — the gentler high-frequency content (compared to white or even pink) is less stimulating to the auditory cortex; many adults with ADHD report brown noise dramatically reduces internal distraction.
Sleep and deep relaxation — the bass-heavy texture resembles distant thunder, ocean surf, or a low ventilation hum, all of which the brain treats as “safe” ambient.
Tinnitus masking — for low-frequency tinnitus the spectral overlap with brown's energy region can provide better masking than higher-pitched noise colours.
Low-frequency speaker / subwoofer testing — brown excites the sub-100 Hz region much more than white or pink, useful for checking sub response, port tuning, and room modes that show up only when you push real energy into the band.

About the “Compare colors” button

Three seconds each of white, pink, and brown in sequence so you can hear the perceptual shift — bright hiss → balanced shower → deep rumble. The slope readout and the visible spectrum reorganise in real time as each colour plays. Each colour uses its own generator: white via Math.random(), pink via Paul Kellet's six-pole IIR cascade (−3 dB/oct), and brown via the leaky integrator described above (−6 dB/oct).

Frequently Asked Questions

Why does the spectrum slope downward instead of being flat?

Because that's the defining property of brown noise — power falls off at −6 dB per octave. On a log-frequency axis, each octave is the same horizontal distance, so the constant −6 dB-per-octave drop shows up as a straight downward line. The cyan dashed reference is the textbook ideal, auto-anchored to the measured level at 1 kHz on the first frame; the live bars should track it closely. The Measured slope readout converges to about −6.0 dB/oct within a few frames.

Is “brown noise” the same as “red noise”?

Yes — the two names are interchangeable. The audio community typically says “brown” (after Robert Brown / Brownian motion); the climate-science and physics communities often say “red” (as the analogue of red light in the optical-frequency analogy). The signal itself is identical.

Why is brown noise so often recommended for ADHD focus?

The conventional explanation: the bass-heavy spectrum gives the auditory cortex a steady, non-stimulating “floor” that masks intrusions without itself becoming an attention magnet. White noise's high-frequency hiss tends to keep the high-frequency-sensitive parts of the auditory system more activated; brown's low-frequency dominance lets those circuits relax. Individual results vary — the Compare button is there precisely so you can pick what works.

Is the 2-second loop noticeable?

Internally the audio plays a 2-second buffer of independently-integrated random samples on loop. Statistically the loop is detectable; perceptually it isn't — brown's spectrum is featureless and the brain has nothing to latch onto. For very long sessions a downloaded 60-second WAV looped with crossfade in a media player has even less periodicity.

What does the “sleep timer” actually do?

Counts down 15, 30, or 60 minutes from when audio actually starts playing (arming it while idle, then pressing Play, resets the countdown). Audio fades smoothly over the last 4 seconds rather than cutting off abruptly. The countdown runs on the browser's wall clock so a brief tab-suspend doesn't drift it; closing the tab cancels it entirely.

Is brown noise safe for long listening?

At moderate levels (typically <50 dB SPL at the listening position) the risk is very low — in some respects brown is gentler than white because the high-frequency energy that drives auditory fatigue is sharply attenuated. The actual risk with any noise is sustained high-volume exposure. Start moderate, increase only to mask intrusions, and keep the source about a metre away rather than next to your ear. For infants the same conservative levels apply.

Will brown noise damage my speakers or subwoofer?

Not at sensible levels. Brown does concentrate energy in the low end, so if you push the volume on a small speaker not designed for sub-bass, you may hear the cone bottoming or the port chuffing — that's mechanical strain, back off. On a properly-rated subwoofer or large monitor, brown at moderate level is no worse than any low-content material (a film score mixed with a lot of LFE, for example).

Does it work offline?

Yes — once the page is loaded, all noise generation, the live spectrum, the sleep timer, and the WAV download work fully offline. Nothing is uploaded or fetched after page load.

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