They don't give exhaust ticket to loud vehicules, they give exhaust ticket for the looks of a "sport/modified" exhaust system, otherwise tons of rusty car/minivans with broken exhaust would be getting these tickets but it never happens.
Rusty vehicule won't be to loud ticket but " non conforme" since the sound come from failure in the system...but yes they will never receive a ticket for that
But most of the time they don't give a to loud ticket since they dont have reference standard and adequate measurment systeme
They try to revert to "non conforme" system checking the physical spec