I had this happen to me Neongirl; about 4 months ago
My exhaust pipe was welded at the catalytic converter. That weld evantually rusted away and separated resulting in huge grumbling rumbly sounds.
I took it to my nearest exhuast shop. They suggested that I get a new cat converter,it was in rough shape. You may not need one.
What they will do its replace a section of the old rusted pipe. They should use a mig welder (sorry if the term is wrong) and cut the rusted pipe away. They will then take a new section of pipe and weld it to the existing exhaust pipe and cat. Sometimes they bolt it as well.
This is a good time to consider a high flow performance cat converter made of stainless steel. If the budget allows for it
Hope this is a start
Diamond White Classic Aurora - Back on the Road
Galaxy Silver Grand Prix GTP CompG - Soon to be mothballed