91 se radio buzz

My 91 SE (3.1 L)has a continual low (but annoying) buzz when (original ) radio is on even when volume is off. There is no buzz when engine is off and radio is playing. This buzz has been noticeable for over a year and has gotten somewhat more noticeable lately. Any ideas what to look for??

get a condenser and plug it on the positive alternator terminal. That will take it off.

get a condenser and plug it on the positive alternator terminal. That will take it off.
Thanks for the info. Will see if it is the answer.