ey TJ i had the Gates timing belt installed in my R33 GTST done by RE customs and its a very slight hum. i could only here it when i was standing in fron of the car trying hard to listen to it. apart fromt hat you cant here it inside your car.
i have a HKS belt in my R34 and ye its loud as f**k and annoying. youll prob here it on the dyno day or if your at RE this arvo lol
but ye Gates timing belt awesome and cheap from just jap