// init() once the page has finished loading.
window.onload = init;

var context;
var buffer;
var duration = 20.0;
var sampleRate = 44100.0;

function init() {
    context = new webkitAudioContext();

    var numberOfFrames = duration * sampleRate;
    buffer = context.createBuffer(1, numberOfFrames, sampleRate);
    var data = buffer.getChannelData(0);

    for (var i = 0; i < numberOfFrames; ++i) {
        data[i] = Math.sin(440.0 * Math.PI * i / sampleRate);
    }

    source = context.createBufferSource();
    source.buffer = buffer;
    source.connect(context.destination);
    source.noteOn();
}