Only show presenter on screen even when participants are speaking without muting.

I need to know how to stop my participants from appearing on screen when they speak.  I want to keep the gallery view during the meeting so I can see anyone, but for the full-screen view, I want to be the only on screen...I don't want them to ever be seen on screen when they speak.  I also don't want them muted...I just want to remain on screen when and while they're speaking.