Funny you should mention that. I just took some video of that same install. They're short, but I think you get the idea.
Nothing in the car is on, so all you hear is the exhaust. A few of them are hard to hear, actually because it's that quiet.
YouTube - Corsas at highway speed
http://www.youtube.com/watch?v=2cuE4QcVpO0
YouTube - Corsas from a light, normal acceleration
YouTube - Corsas from a light, hard acceleration
Hope this helps.