fadeIn(duration, loop, marker)
Starts this sound playing (or restarts it if already doing so) and sets the volume to zero.Then increases the volume from 0 to 1 over the duration specified. At the end of the fade Sound.onFadeComplete is dispatched with this Sound object as the first parameter,and the final volume (1) as the second parameter.
Parameters
Name Type Argument Default Description duration number <optional> 1000 The time in milliseconds over which the Sound should fade in