Q: Car rumbles and vibrates

A rumbling sound could be associated with a lot of different things. Being that you are able to hear it on the exhaust piping is good because the causes can be narrowed down. Depending on the mileage the chance of your catalyst failing increases with more miles on the motor. One possibility could be that the catalyst started to break down and broke into pieces. When this happens pieces of the catalyst can be scattered throughout the exhaust system causes rattles at multiple different places. Heat shielding is also used along the entire system and can come loose causing the same problem. A proper inspection the vehicle should be carried out by a qualified technician, like the ones at YourMechanic, in order to quickly get to the source of your concern with the noise coming from the exhaust and get it fixed right the first time.