One thing though, at that time the drivers were wearing a helmet and had cotton wool in the ears, i think they heard muffled sounds.
I'd love to hear something similar in my headphones
This is true with nearly all sims, but most people expect/prefer to hear the external sound when driving. A more correct sound is easily achieved using a low-pass filter with about a 12dB/octave rolloff above 2-3kHz (the rolloff point will determine how muffled the sound becomes, 1.5-2k for a modern full-face helmet, higher for older styles ...basically adjust for what you like). In sims with misfire sounds those also need to be subdued but the procedure is different since the spectrum is less important than the waveshape, fortunately these are small, easily edited files; reduce the dynamic range and rise time of the signal so the "pop" sound becomes more of a "thump".