In general, from my real life experience and many videos too (I know videos don't mean crap, but MANY seemed to verify my real life experiences), if the car is right alongside you and you're right near the exhaust or if it's right in from of you very close you can hear it, but the volume of the other car, from your point of view, decreases very quickly as it goes further away from you. It goes from like max volume to fully muted in a very short distance.
Also, you DEFINITELY don't hear cars behind you coming up, and you DEFINITELY don't hear cars coming towards you on the other part of the track when you guys are heading towards each-other