The exhaust is very, very loud! Passengers often complain but I think it sounds awesome :) It's about 108 dB @ 4500rm 3/4 of a meter @ 45 degrees away from the exhaust!
Very nice shot. Passengers? Hand 'em a set of earplugs and drive on. Open air cars were not meant to be quiet. Neither were fast ones. Combined? Forget it! Earplugs.