2001 Ford Ranger

Noises problem
2001 Ford Ranger 6 cyl Four Wheel Drive Automatic 48000 miles

I recently bought my truck and just before I bought it they replaced the catalytic converter. It sounded great at first but now when you accelerate it makes a weird exhaust noise. It also does it when you start it. It is not affecting my gas mileage or anything but it is annoying. Is there something that they could have missed? Does it have more than one to it? Anything is helpful.
October 10, 2008.

Have the exhaust system checked possible clamp or a hanger
also check the EX shield
also check the catalytic converter it self

Oct 11, 2008.