droning noise heard inside cabin around transmission hump on 1999 Chevrolet Camaro

issue seems to be related to charging system, however,noise is not comming from alternator. if single lead to alternator is disconected, noise disappears. noise only heard in cabin and is very annoying.issue started at around 16k. thanks

Asked by for the 1999 Chevrolet Camaro
ck tensioner and idler pulleys