invert polarity

gistfile1.js

var url = 'monoSound.wav'
  , audio = new Audio(url)
  , context = new webkitAudioContext()
  , processor = context.createJavaScriptNode(512, 1, 1)
  , sourceNode

audio.addEventListener('canplaythrough', function(){
  sourceNode = context.createMediaElementSource(audio)
  sourceNode.connect(processor)
  processor.connect(context.destination)
  audio.play()
}, false)

processor.onaudioprocess = function(evt){
  var input = evt.inputBuffer.getChannelData(0)
    , output = evt.outputBuffer.getChannelData(0)
    , len = input.length
    , i = 0
  for ( ; i < len; i++ ) output[i] = -1 * input[i]
}