Is it possible to give a quiet engine more character and noise?

I want to buy a modern Triumph Bonneville, the ones based on the old British clics. They look great but the only thing that lets them down is the engine noise lacks character... it's too quiet, it doesn't roar... to be honest it just sounds... tinny. What is it that makes a modern engine quiet? I'd imagine that a mechanism with several thousand small petrol explosions every minute is inherently noisy. Is there any modifications that can be made to it to make it sound louder?