I think there's a difference here between engine and exhaust. With F1 cars I suspect spectators wouldn't hear the engines of the cars passing even if they had silent exhausts. Modern cars have such good insulation you can no longer hear the exhaust and engine noises so well so some manufacturers have started playing engine noises through the speakers. Exhaust noise has been tweaked for years: Ferrari, Aston, Audi and especially AMG long ago established the kind of noises that attract other men and play it at volume out of their cars' exhausts.