I have one of these belts on my own car as well, there are two different gates belts as far as i am aware, the one i have is the "race" version and is blue, it makes a light whirring noise, although your seems louder, or it could just be that my car runs a solid top end and jun cams which are quite loud and it may not be as noticeable.
provided the tension of the belt is ok, i cant see there being a problem, apparently very strong belts, hence the noise, but i wouldn't buy another one, the nismo seems to have the best rap, or genuine