dtmf.js

var DTMF = function () { this.init.apply(this, arguments) };
DTMF.prototype = {
    table : {
        "1" : [697, 1209], "2" : [697, 1336], "3" : [697, 1477], "A" : [697, 1633],
        "4" : [770, 1209], "5" : [770, 1336], "6" : [770, 1477], "B" : [770, 1633],
        "7" : [852, 1209], "8" : [852, 1336], "9" : [852, 1477], "C" : [852, 1633],
        "*" : [941, 1209], "0" : [941, 1336], "#" : [941, 1477], "D" : [941, 1633]
    },

    init : function (context, opts) {
        this.context = context || new AudioContext();
        this.sendingTime = 100e-3;
        this.minimumPause = 60e-3;
        // sine を2個合成するので、半分にしとかないとクリッピングして歪みます
        this.gain = this.context.createGain();
        this.gain.gain.value = 0.5;
        this.gain.connect(this.context.destination);
    },

    play : function (str) {
        str = str.toUpperCase().replace(/-/g, '');
        if (!str.match(/^[1234567890ABCD*#]*$/)) throw "invalid string";

        this.nodes = [];
        var pos = this.context.currentTime; 
        for (var i = 0, len = str.length; i < len; i++) {
            var tone = this.table[str.charAt(i)];
            var oscLow = this.context.createOscillator();
            oscLow.frequency.value = tone[0];
            oscLow.connect(this.gain);

            var oscHigh = this.context.createOscillator();
            oscHigh.frequency.value = tone[1];
            oscHigh.connect(this.gain);

            oscLow.start(pos);
            oscHigh.start(pos);

            pos += this.sendingTime;

            oscLow.stop(pos);
            oscHigh.stop(pos);

            this.nodes.push([ oscLow, oscHigh ]); // retain

            pos += this.minimumPause;
        }
        return pos - this.context.currentTime;
    }
};