Brad I'll explain it this way...
One of the starting dudes at Willow (I think his name is Denny but I always forget???) put his hands over his ears at a recent event whenever I pulled off the line with the open pipes
I have a 2-in, 2-out Dansk SS sport muffler as well, and when that is on the car, honestly I can barely hear it from inside over the carbs and other ambient noise. You can hear and feel the megaphones even with your helmet on.