***UPDATE***I narrowed down noise to 1 extension. Pulled it off of block. No noise for several days. Now every once in awhile they hear it very briefly. I'm counting on the receptionist to monitor frequency/volume,etc...
We still are not sure if it increases in porportion to number of calls. It seems to be worse in the morning when they are busiest/on the tele. the most???Thank you all. I disconnected the MOH at the beginning of this adventure; to answer last post.