Tone.js/Tone/source/Noise.js

///////////////////////////////////////////////////////////////////////////////
//
//  NOISE
//
///////////////////////////////////////////////////////////////////////////////
define(["Tone/core/Tone"], function(Tone){

    //@param {string} type the noise type
    Tone.Noise = function(type){
    	//extend Unit
    	Tone.call(this);

    	//components
    	this.jsNode = this.context.createScriptProcessor(this.bufferSize, 0, 1);

    	//connections
        this.jsNode.connect(this.output);

    	this.setType(this.defaultArg(type, "white"));
    }

    Tone.extend(Tone.Noise, Tone);

    //@param {string} type ('white', 'pink', 'brown')
    Tone.Noise.prototype.setType = function(type){
    	switch (type){
    		case "white" : 
    			this.jsNode.onaudioprocess = this._whiteNoise.bind(this);
    			break;
    		case "pink" : 
    			this.jsNode.onaudioprocess = this._pinkNoise.bind(this);
    			break;
    		case "brown" : 
    			this.jsNode.onaudioprocess = this._brownNoise.bind(this);
    			break;
    		default : 
    			this.jsNode.onaudioprocess = this._whiteNoise.bind(this);
    	}
    }

    //modified from http://noisehack.com/generate-noise-web-audio-api/
    Tone.Noise.prototype._pinkNoise = (function() {
        var b0, b1, b2, b3, b4, b5, b6;
        b0 = b1 = b2 = b3 = b4 = b5 = b6 = 0.0;
        return function(e) {
            var bufferSize = this.jsNode.bufferSize;
            var output = e.outputBuffer.getChannelData(0);
            for (var i = 0; i < bufferSize; i++) {
                var 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; // (roughly) compensate for gain
                b6 = white * 0.115926;
            }
        }
    })();

    //modified from http://noisehack.com/generate-noise-web-audio-api/
    Tone.Noise.prototype._brownNoise = (function() {
        var lastOut = 0.0;
        return function(e) {
            var bufferSize = this.jsNode.bufferSize;
            var output = e.outputBuffer.getChannelData(0);
            for (var i = 0; i < bufferSize; i++) {
                var white = Math.random() * 2 - 1;
                output[i] = (lastOut + (0.02 * white)) / 1.02;
                lastOut = output[i];
                output[i] *= 3.5; // (roughly) compensate for gain
            }
        }
        return node;
    })();

    //modified from http://noisehack.com/generate-noise-web-audio-api/
    Tone.Noise.prototype._whiteNoise = function(e){
        var bufferSize = this.jsNode.bufferSize;
        var output = e.outputBuffer.getChannelData(0);
        for (var i = 0; i < bufferSize; i++) {
            output[i] = Math.random() * 2 - 1;
        }
    }

    return Tone.Noise;
});