{Hell, Barker not only made it work, he was tethered to a wired mic for how many years?)
He not only made it work, but Bob was a master at using the cord to direct the contestant to exactly where he wanted them and mostly keep them there, kind of like an invisible barrier.
When offered to upgrade to a cordless mike, Bob turned it down.
He was so good at it that unless you were paying attention, you don't really notice it.
Somebody can correct me if I'm wrong, but I believe there was a mic up there in the past anyway.
Yes, there is a microphone embedded in the top of the gameboard to pick up contestant reaction and the "plinking" sound.