There is a common practice among tuners called sound offs. This basically means you dust off your tuner car which has an aftermarket exhaust and see if it sounds better than another.
All in all, this isn’t that much of competition, as apart from decibels, you can’t really establish any rules, and more noise doesn’t always mean better.
Also most of the times, these battles take place with the vehicles stationary, and that isn’t really the way to go if you want to see how nice an engine purrs. Still, for a couple of minutes, you can have a bit of fun with it. Especially if you just completed a nice day at the track.
This is exactly what happened with the owners of these M3s, which decided to show off their exhaust systems after a 2.5 hour race. Between a couple of Dinan exhaust systems and one from AUTOCouture Motoring, they all sound rather nice, but if you want me pick one and say that one is the best, I cannot.