function createDCOffset() {
  var ac = main.audiocontext;
  var buffer = ac.createBuffer(1, 2048, ac.sampleRate);
  var data = buffer.getChannelData(0);
  for (var i = 0; i < 2048; i++) data[i] = 1.0;
  var bufferSource = ac.createBufferSource();
  bufferSource.buffer = buffer;
  bufferSource.loop = true;
  return bufferSource;
}
Set the width of a Pulse object (an oscillator that implements
 Pulse Width Modulation).

 @method  width
 @param {Number} [width]    Width between the pulses (0 to 1.0,
                        defaults to 0)