Add pink, white and brown oscillators

packages/superdough/synth.mjs

@@ -20,8 +20,11 @@ const fm = (osc, harmonicityRatio, modulationIndex, wave = 'sine') => {
   return mod(modfreq, modgain, wave);
 };
 
+
 export function registerSynthSounds() {
-  ['sine', 'square', 'triangle', 'sawtooth'].forEach((wave) => {
+  ['sine', 'square', 'triangle',
+    'sawtooth', 'pink', 'white',
+    'brown'].forEach((wave) => {
       registerSound(
         wave,
         (t, value, onended) => {
@@ -63,7 +66,6 @@ export function registerSynthSounds() {
             vibmod,
             partials: n,
           });
-
           // FM + FM envelope
           let stopFm, fmEnvelope;
           if (fmModulationIndex) {
@@ -146,9 +148,57 @@ export function waveformN(partials, type) {
   return osc;
 }
 
+export function getNoiseOscillator({ t, ac, type = 'white' }) {
+  const bufferSize = 2 * ac.sampleRate;
+  const noiseBuffer = ac.createBuffer(1, bufferSize, ac.sampleRate);
+  const output = noiseBuffer.getChannelData(0);
+  let lastOut = 0;
+  let b0, b1, b2, b3, b4, b5, b6;
+  b0 = b1 = b2 = b3 = b4 = b5 = b6 = 0.0;
+
+  for (let i = 0; i < bufferSize; i++) {
+    if (type === 'white') {
+      output[i] = Math.random() * 2 - 1;
+    } else if (type === 'brown') {
+      let white = Math.random() * 2 - 1;
+      output[i] = (lastOut + (0.02 * white)) / 1.02;
+      lastOut = output[i];
+    } else if (type === 'pink') {
+      let 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;
+      output[i] *= 0.11;
+      b6 = white * 0.115926;
+    }
+  }
+
+  const o = ac.createBufferSource();
+  o.buffer = noiseBuffer;
+  o.loop = true;
+  o.start(t);
+
+  return {
+    node: o,
+    stop: (time) => o.stop(time)
+  };
+}
+
 export function getOscillator({ s, freq, t, vib, vibmod, partials }) {
   // Make oscillator with partial count
   let o;
+
+  if (['pink', 'white', 'brown'].includes(s)) {
+    let noiseOscillator = getNoiseOscillator({ t: t, ac: getAudioContext(), type: s })
+    return {
+      node: noiseOscillator.node,
+      stop: noiseOscillator.stop
+    }
+  } else {
     if (!partials || s === 'sine') {
       o = getAudioContext().createOscillator();
       o.type = s || 'triangle';
@@ -178,4 +228,6 @@ export function getOscillator({ s, freq, t, vib, vibmod, partials }) {
         o.stop(time);
       },
     };
+  }
 }
+