When Jack demonstrates the hidden cameras to Greg, the images on the TV were silent. However in the final scene of the film, where Jack is watching Greg, he can here every word he says. Even though there are no hidden microphones.
Or maybe where he is demonstrating, the volume is up but you can't hear it because Greg is talking at the same time, so it just sounds like one person speaking, when, in fact, it is him and the TV. Understand? Didn't think so.
When they were getting filmed and speaking it was similtaneous so you wouldn't hear them speaking on the tv because they are saying the same thing in life as on the tv similtaneouly and there is no delay on the tv if you get me and if yu don't get me well im really cad at explaining things.