As a motorcyclist & car driver, what I've observed is in a car you can hear loud pipe bikes- but only when they are in front of you, i.e. with the tailpipe poin

As a motorcyclist & car driver, what I've observed is in a car you can hear loud pipe bikes- but only when they are in front of you, i.e. with the tailpipe pointing at your face. Behind or beside you- in other words, in your blind spots- don't hear a thing.