Do motorcycle helmets allow you to hear your surroundings? That's another serious question by the way as I've never worn one. Plus, not many cars make such a noise as the motorbike I heard.
Like cycle helmets, motorcycle helmets vary. A lot of it is about fit. Theoretically, more expensive helmets are designed to reduce wind noise. In reality it's a bit more random than that.
Some bikes have screens, some do not. Depending on rider height, you can have varying degrees of wind noise and buffeting with them.
Some of the worst culprits in my experience have been full enclosure helmets, with random whistling or wind roar. No wonder some riders wear ear plugs! Open face helmets I have found to be quieter which seems to be counter intuitive. Perhaps due to padding round the ears which keeps the wind out. Despite all that, I've found that at round town speeds when you are most likely to be mingling with traffic I can hear my surroundings quite well whatever the helmet.
An open face helmet is helpful here as your peripheral vision is not restricted. Primary safety, eg open face helmet increasing awareness, able to look downwards easily, ability to talk to people, helpful in avoiding accidents, vs secondary safety, eg full enclosure helmet potentially minimising damage should you have one.
Being a glasses wearer I've never liked full enclosure helmets much, but fortunately there's a middle course since flip front helmets were developed, combines the benefits of both types. Flip up for round town, flip down out of town.
If your bike is sounding a bit rattly and in need of a tune up, buying a new helmet can transform the sound of it as old padding gradually compresses and lets in sound. A new helmet is tight until it beds in, and damps down the sound. So if the noisy rider in the OP bought a new helmet, he might take a drill to his exhaust to keep what he hears to the same level while annoying even more people!
