As Sportsmail first reported last year, the lack of crowd noise in behind-closed-doors matches led clubs to warn their players and managers over the use of foul language — given the increased chances that it would be picked up by broadcasters.
It has also allowed those present to hear instructions and 'banter' between coaching staff.
There have been some memorable episodes, including at Manchester United's 9-0 thrashing of Southampton when, after Luke Shaw had set up Aaron Wan-Bissaka for the first to notch an assist, coach Darren Fletcher announced to the bench he was delighted because Shaw was 'in my fantasy team'.