Pink Noise

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What Is This Sound?

This is pink noise — a balanced, full-spectrum noise signal where each octave carries equal energy. Unlike white noise, which sounds bright and hissy, pink noise has a warmer, more natural character that many people find more pleasant for extended listening.

Pink noise is sometimes called 1/f noise or flicker noise because its power is inversely proportional to frequency. You will find this pattern everywhere in nature: ocean waves, heartbeat rhythms, wind through trees, and even fluctuations in the stock market all follow a 1/f distribution. This ubiquity may explain why pink noise sounds so inherently natural and soothing to human ears.

How Is Pink Noise Created with Code?

Tone.js makes generating pink noise straightforward. The library applies an internal filtering algorithm to shape white noise into a 1/f spectrum.

The Complete Signal Chain

import * as Tone from "tone";

// Create a pink noise source
const noise = new Tone.Noise("pink");

// Set output level — pink noise is perceived as quieter
// than white noise at the same amplitude, so we boost it
const gain = new Tone.Gain(0.3);

// Connect: Noise → Gain → Output
noise.connect(gain);
gain.toDestination();

// Start the noise
noise.start();

The Tone.Noise("pink") constructor generates white noise internally, then processes it through a series of IIR (Infinite Impulse Response) filters to produce the characteristic -3dB per octave slope.

The Paul Kellet Filter Algorithm

Under the hood, most Web Audio implementations of pink noise use a variant of the Paul Kellet algorithm, which applies a carefully tuned set of first-order IIR filters to white noise:

// Simplified Paul Kellet pink noise filter
let b0 = 0, b1 = 0, b2 = 0, b3 = 0, b4 = 0, b5 = 0, b6 = 0;

for (let i = 0; i < bufferSize; i++) {
  const white = Math.random() * 2 - 1;
  b0 = 0.99886 * b0 + white * 0.0555179;
  b1 = 0.99332 * b1 + white * 0.0750759;
  b2 = 0.96900 * b2 + white * 0.1538520;
  b3 = 0.86650 * b3 + white * 0.3104856;
  b4 = 0.55000 * b4 + white * 0.5329522;
  b5 = -0.7616 * b5 - white * 0.0168980;
  output[i] = (b0 + b1 + b2 + b3 + b4 + b5 + b6 + white * 0.5362) * 0.11;
  b6 = white * 0.115926;
}

Each filter state variable (b0 through b6) has a different time constant, collectively producing a remarkably accurate -3dB/octave slope across the audible range.

The Science Behind Pink Noise

The 1/f Spectrum

Pink noise is defined by a power spectral density that decreases inversely with frequency: S(f) = 1/f. In practical terms, this means the energy drops by 3 decibels for every doubling of frequency (every octave). The result is equal energy per octave — the octave from 100Hz to 200Hz contains the same total power as the octave from 1kHz to 2kHz.

This is precisely what makes pink noise sound balanced to our ears. Human hearing perceives frequency logarithmically (in octaves), so a signal with equal energy per octave sounds spectrally even, whereas white noise (equal energy per hertz) sounds tilted toward the high end.

Why 1/f Is Everywhere

The 1/f pattern appears across an astonishing range of natural and human-made systems: the fluctuations in river flow, the timing of neural firing, loudness variations in music, and even the distribution of earthquakes by magnitude. Researchers have proposed many theoretical explanations, from self-organized criticality to superpositions of relaxation processes, but no single universal mechanism has been established. What is clear is that 1/f signals occupy a sweet spot between the complete randomness of white noise and the excessive correlation of brown noise.

Perceptual Balance

Because pink noise distributes energy equally across octaves, it aligns closely with how humans perceive loudness across the frequency spectrum. Audio engineers use pink noise as a calibration signal for equalizing sound systems — if a system reproduces pink noise and it sounds even across the spectrum, the system is well-calibrated for music and speech.

Common Uses

• Sleep & Relaxation — Studies suggest pink noise may enhance deep sleep when played at low volume during the night, potentially improving memory consolidation
• Sound System Calibration — The standard reference signal for equalizing PA systems, studio monitors, and home audio setups
• Focus & Study — The balanced spectrum masks distractions without the harshness of white noise, making it comfortable for hours of listening
• Audio Mastering — Used as a spectral reference when making equalization decisions in music production
• Acoustic Measurement — Employed in room acoustics analysis because its per-octave energy distribution matches how we measure sound
• Meditation & Mindfulness — The warm, ocean-like quality provides a calming ambient backdrop

Technical Details

Frequently Asked Questions

What is the difference between pink noise and white noise?

White noise has equal energy per hertz, which makes it sound bright and hissy. Pink noise has equal energy per octave (−3dB/octave slope), which makes it sound warmer and more balanced. Most people find pink noise more pleasant for extended listening.

Is pink noise better than white noise for sleep?

Research is ongoing, but several studies have found that pink noise played during sleep may improve sleep quality and memory. The balanced spectrum is generally perceived as less harsh than white noise, which may make it more comfortable for overnight use.

Can I use this sound commercially?

Yes. The sound is generated in your browser using code. The WAV file you download is free to use in any personal or commercial project.

Why is it called “pink” noise?

The name comes from the analogy with light. If you filtered white light to reduce the higher-frequency (blue) end of the spectrum, the result would appear pinkish. Similarly, pink noise is white noise with the higher audio frequencies reduced.