You should see it and hear it live. No video really does it justice. The music from the gun comes in three parts. The sonic whine, the earth's rumbling surrender and the dragon's firey breath.
Not in person. It sounds like the chainsaw of freedom.
We also had annual air shows at RG-AFB, and getting to see the A-10s maneuver was really incredible. It was amazing how quiet those planes are when they're coming at you,but holy crap, they're LOUD when they overfly you! Of course, there were no live fire exercises at the airshow, which was something of a let-down.
While I've never experienced the 30mm cannon, I used to do a lot of work out at Lake City Army Ammunition Plant, and I used to hear test fire of the 20mm Gatling cannons, and that was incredible. I can only imagine what the 30mm sounds like.
Mark