Chains make noise too, people are just used to hearing them, also belts. There is a friction but again, it's going to be there regardless. The issue is harmonics through the crank. I did some research on this myself and i got pros and cons, mostly about the harmonics through the crank though. Most said they would definitely run them on a race engine but not on a street engine. I'm considering going with one on my next engine, since it's only driven on the weekends anyways.