Yeah i just bought an H100i and have the identical issue. I actually replaced mine in store and both made the noise. Not really sure what to make of it since my NZXT coolers never do this.
The only 'fix' is to put the profile of the cooler on Extreme. But that's not a permanent solution.
Edit: I was just reading online, and someone discovered that possibly plugging the cooler fans directly into the motherboard instead of the cooler adapter might fix it. So you might want to give that a try, I'm going to see if that does anything. Apparently the power draw from the fans might be causing the pump to make that noise.
