I work in a Internet broadcasting distance learning center. I've read your technical bulliten on distance learning. Do you have any suggestions on how to filter out the noise of a projector that hangs on a ceiling?
Sorry, the noise from the projector is acoustical. A microphone cannot sort out the acoustical noise you do want (speech) from the acoustical noise you do not want (the projector).
A unidirectional microphone might be useful if the rear of the mic can be pointed at the projector.