WavepotWindchimes.js

/*!
 *
 * wavepot windchimes
 * nondefault.net
 *
 */
 
var transpose = 0;
 
var ct = 0;
var chimes = []; //stores chimes that are being played
 
//a single chime note
chimes.push({
  "start": 0,
  "len": 1,
  "freq1": 200,
  "freq2": 400
});
 
//DSP function outputs sound wave height at time t
function dsp(t) {
  //occasionally add a new chime
  if (t-ct>1) {
    ct = t-Math.random()*0.6;
    chimes.push(makeRandomChime(t));
  }
  
  var dspOut = 0; //sum of all chime sounds being played right now
  var cl = chimes.length; //number of chimes
 
  for (var i=cl-1; i>=0; i--) {
    if (chimes[i]!==null) {
      dspOut += chime(chimes[i], t); //add this chime sound
      if (t > chimes[i].start + chimes[i].len) { //remove this chime sound from the array if it's done playing
        chimes[i] = null;
      }
    }
  }
  
  return dspOut*0.15                                                                           //chimes at 15% volume
    +brownNoise()*(0.04*Math.abs(Math.sin(t*0.24)+Math.sin(t*0.6)+Math.sin(t*0.014))+0.02)     //wind or waves or something
    +rain()*0.6;                                                                               //rain
}
 
//add a chime
function makeRandomChime(t) {
  var freq = note(~~(Math.random()*7)*2+24);
  return {
    "start": t,
    "len": Math.random()*2+2,
    "freq1": freq,
    "freq2": freq*(1/5)
  };
}
 
function chime(props, t) {
  var wave1 = sin(props.freq1, t); //note #1
  var wave2 = sin(props.freq2, t); //note #2
  var wave3 = sin(props.freq1*0.01, t); //a sort of ringing effect
  
  //mix the three sounds
  return decayf(wave1, props.start, props.len, t)*
         decayf(wave2, props.start, props.len, t)*
         (1+decayf(wave3, props.start, props.len, t)*0.2);
}
 
//sin
function sin(x, t){
  return Math.sin(2 * Math.PI * t * x);
}
 
//brownian noise generator
var brownNoise = Brownian();

function Brownian() {
  var lnoise = 0.5;
  return function() {
    var n = Math.random()*2-1;
    var v = (lnoise + (0.02 * n)) / 1.02;
    lnoise = v;
    return v*3.5;
  }
}

//rain generator
var np = 0.5;
var rainlp = FastLP(10);
var rainNoise = Brownian(), rainNoise2 = Brownian();
function rain() {
  var n = rainNoise()*rainNoise2();
  var val = Math.abs(n-np)<0.04?n:0;
  np = n;
  return rainlp(val);
}
 
//decay function.  Return value wave decayed from start s for length l seconds, at time t. 
function decayf(wave,s,l,t) {
  return Math.max(0,1-(t-(s))/l)*wave - Math.max(0,1-(t-s)/0.01)*wave;
}
 
// gets note `n` frequency of `octave`
function note(n, octave){
  n += transpose;
  return Math.pow(2, (n - 33 + (12 * (octave || 0))) / 12) * 440;
}

function FastHP(n){
  var value = 0;
  return function(x){
    return value += x - value * n;
  };
}

function FastLP(n){
  var value = 0;
  return function(x){
    return value += (x - value) / n;
  };
}