The audio trigger does what it sounds like it does, the camera's built in mic hears a set db and triggers the camera to fire. The delay is pretty minimal and so I am able to experiment with high speed photography. Now mind you, the delay cannot be adjusted, only the db level.
The image above is of a lit light bulb exploded using a pellet gun. The camera was set several feet away and zoomed in with a 70-300mm lens. A speedlight was set up to camera right, about 3 feet from the bulb. I stood several feet from the bulb and fired directly at it. The camera was fired upon hearing the trigger pull of the pellet gun. It was processed in Lightroom 4 only.