My DKW 3=6 Panoramic Coupe (so-called because of it's wrap-around rear window, ala the '51 Studebaker) is actually a pillar-less version of the 2-door sedan, with a rounded body that somewhat resembles a '50s Morris Minor. The holy-grail for postwar DKW collectors is the SP1000 coupe and convertible that DKW built from 1958 to 1963 and styled to resemble the '57 T-Bird.
As for the sound, 'popcorn popper' is how it's usually described!

Happy Motoring, Mark

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DrDKW