A loud exhaust is the obvious symptom. It is not always the expensive one.
Most exhaust noise comes from a rusted joint or a failed hanger rather than the muffler itself, and those are straightforward repairs.
The leak you cannot hear is the one upstream of the oxygen sensors. It throws off fuel trim and costs you real fuel economy while everything sounds perfectly normal.
Illinois winters and road salt are hard on exhaust systems. We check yours whenever the car is up.