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AutoWah effect

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Yotam Mann 2014-08-23 14:23:43 -04:00
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commit 3b08ef6997
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Tone/effect/AutoWah.js Normal file
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define(["Tone/core/Tone", "Tone/component/Follower", "Tone/signal/ScaleExp", "Tone/effect/Effect"], function(Tone){
/**
* @class AutoWah connects an envelope follower to a bandpass filter.
* Some inspiration from Tuna.js https://github.com/Dinahmoe/tuna
*
* @constructor
* @extends {Tone.Effect}
* @param {number=} [baseFrequency=100] the frequency the filter is set
* to at the low point of the wah
* @param {number=} [octaves=5] the number of octaves above the baseFrequency
* the filter will sweep to when fully open
* @param {number=} [sensitivity=0] the decibel threshold sensitivity for
* the incoming signal. Normal range of -40 to 0.
*/
Tone.AutoWah = function(baseFrequency, octaves, sensitivy){
Tone.Effect.call(this);
/**
* the envelope follower
* @type {Tone.Follower}
* @private
*/
this._follower = new Tone.Follower(0.15, 0.5);
/**
* scales the follower value to the frequency domain
* @type {Tone}
* @private
*/
this._sweepRange = new Tone.ScaleExp(0, 1, 0, 1, 2);
/**
* @type {number}
* @private
*/
this._baseFrequency = this.defaultArg(baseFrequency, 100);
/**
* @type {number}
* @private
*/
this._octaves = this.defaultArg(octaves, 5);
/**
* @type {BiquadFilterNode}
* @private
*/
this._bandpass = this.context.createBiquadFilter();
this._bandpass.type = "bandpass";
this._bandpass.Q.value = 2;
/**
* @type {BiquadFilterNode}
* @private
*/
this._peaking = this.context.createBiquadFilter();
this._peaking.type = "peaking";
this._peaking.gain.value = 20;
//the control signal path
this.chain(this.effectSend, this._follower, this._sweepRange);
this._sweepRange.connect(this._bandpass.frequency);
this._sweepRange.connect(this._peaking.frequency);
//the filtered path
this.chain(this.effectSend, this._bandpass, this._peaking, this.effectReturn);
//set the initial value
this._setSweepRange();
this.setSensitiviy(this.defaultArg(sensitivy, 0));
};
Tone.extend(Tone.AutoWah, Tone.Effect);
/**
* set the number of octaves that the filter will sweep
* @param {number} octaves the number of octaves above the base frequency the filter will sweep
*/
Tone.AutoWah.prototype.setOctaves = function(octaves){
this._octaves = octaves;
this._setSweepRange();
};
/**
* set the number of octaves that the filter will sweep
* @param {number} octaves the number of octaves above the base frequency the filter will sweep
*/
Tone.AutoWah.prototype.setBaseFrequency = function(baseFreq){
this._baseFrequency = baseFreq;
this._setSweepRange();
};
/**
* set the sensitivity to control how responsive to the input signal
* the wah is.
*
* @param {number} sensitivy the sensitivity to the input signal in dB
*/
Tone.AutoWah.prototype.setSensitiviy = function(sensitivy){
this._sweepRange.setInputMax(this.dbToGain(sensitivy));
};
/**
* sets the sweep range of the scaler
* @private
*/
Tone.AutoWah.prototype._setSweepRange = function(){
this._sweepRange.setOutputMin(this._baseFrequency);
this._sweepRange.setOutputMax(Math.min(this._baseFrequency * Math.pow(2, this._octaves), this.context.sampleRate / 2));
};
/**
* pointer to parents dispose method
* @private
*/
Tone.AutoWah.prototype._effectDispose = Tone.Effect.prototype.dispose;
/**
* clean up
* @return {[type]} [description]
*/
Tone.AutoWah.prototype.dispose = function(){
this._effectDispose();
};
return Tone.AutoWah;
});