Reverb: <input type='checkbox' id='ReverbCheck'><p>
<button id='Start'>start</button>
<script>
  var context = new AudioContext()
  var source = new OscillatorNode(context,{type:'sine'})
  var amplitude = new GainNode(context,{gain:0})
  var impulse=impulseResponse(3,1)
  var convolver = new ConvolverNode(context,{buffer:impulse})
  source.connect(amplitude)
  source.start()
  Start.onclick = function() {
    context.resume()
    amplitude.disconnect()
    convolver.disconnect()
    if (ReverbCheck.checked) {
      amplitude.connect(convolver)
      convolver.connect(context.destination)
    }
    else amplitude.connect(context.destination)
    amplitude.gain.value=1
    amplitude.gain.setValueAtTime(0,context.currentTime+0.05)//pulse lasts 50 ms
  }
  function impulseResponse(duration,decay) {
    var length = context.sampleRate * duration
    var impulse = context.createBuffer(2,length,context.sampleRate)
    var IR = impulse.getChannelData(0)
    for (var i=0;i<length;i++) IR[i] = (2*Math.random()-1)*Math.pow(1-i/length,decay)
    return impulse
  }
</script>