Radio Check then ambient noise

[Spoolin]

When I start iRacing, CrewChief also starts. He says "Radio Check" and then I hear a lot of background ambient noise. This goes away after I pull out of the pits.
Any idea why this happens and how to turn it off?

Even when not in a game. If I start CrewChief I also hear the sound after "Radio Check" but that does go away after 1-2 seconds.

Besides this everything else works fine.