def fadeIn(sound: StereoSound, fadeLen: Int): StereoSound = {
    var soundLeft = ArrayBuffer[Int]()
    var soundRight = ArrayBuffer[Int]()
    val fade = {
      if(fadeLen < 0) 0
      else if(fadeLen > sound.right.size) sound.right.size
      else fadeLen
    }
     for(i <- 0 until sound.left.length) {
       soundLeft += (sound.left(i) * (i / fade.toDouble)).toInt
       soundRight+= (sound.left(i) * (i / fade.toDouble)).toInt
      }

    new StereoSound(soundLeft, soundRight)

  }