I've done the same thing years ago with 3" vanes...same sound. I video'd the shot coming at you at 20, 30 and 40 yards as well as halfway as the arrow whizzed past the camera.

That led me to believe that the deer hear the arrow more than they do the bow at times and why I'd sooner have a 40 yard shot than I would a 20 yard shot at times on nervous deer...seriously.