Actually, it is the shouting to communicate things like "bathroom" over the noise.
I saw an indoor electric kart race in February that was absolutely insane. And everyone in the stadium was able to talk at a normal level.
That was a good time!
You can talk when all cars passed by until next lap.
That should be enough.
Ah I remember my first Formula 1 race live at the track of Monza 1999.
It was really similar like in this video it is even exactly the same place.
I must say this was amazing when you are standing just 3-5 meters away of the cars the sound is much more impressive than anything else.
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http://www.youtube.com/watch?v=7hUFCTLGcgs[/youtube]