I've always used in ear moulded earplugs, as do the vast majority of motorcyclists. I'd happily wear a set of ear defenders in an open car, after all they don't make you deaf to all noise, but rather they're decibel attenuators. They do make your ears horribly sweaty, however. The moulded earplugs don't, but they do get annoying after many hours on a tour, and prompt a nice stop and rest. Hearing is too valuable to lose, though..
