Echoes during pledge drive

Whenever there is a fund drive I can hear an awful echo. I have a good HD receiver. The echo only appears when announcers are asking for money. The music portion of the program comes in fine. The effect drives me nuts when ever there is a pledge drive. The last pledge drive I thought it was me or my equipment. It went away as soon as the drive was over now its back again.
Has anyone else experienced this?

"Echoes"

What it sounds like is the ambiance of the phone room, with its hollow nature creating a echo of sorts, due to the microphone in the phone room being live during the pledging.