MPower.com gives us a deep dive look into the M4's exhaust system courtesy of an interview with Chief Noise Making M engineer Rainer Drees.
Rainer Drees: I am responsible for the acoustic characteristics of M automobiles. This relates to everything that the driver hears as well as everything that can be perceived in the surroundings.
One of my jobs is to ensure that our M cars sound authentic and full of character while at the same time meeting the various worldwide regulations regarding external noise levels. This is above all a matter that concerns the design of exhaust systems.