I recently heard a slight whining noise coming from the undercarriage area. After a day or two it started getting louder. It is now very noticible. I think it is coming from the catalytic converter. Does this sound like a bad catalytic converter or possibly something else?

Also, since researching prices I have read about manufacturers being required to replace bad catalytic converters when under 50K miles. Any truth to this?

Thans in advance for any information.