I actually bought this fan yesterday and am fairly pleased with it. Here are my descriptions of its noise:
500-1000rpm- quieter than my Noctua NF P14s (near silent) at 500rpm but can be heard slightly at 1000rpm, in a fully enclosed case (my case is fully meshed on both sides....lol) I doubt it will be audible
1000- 1500rpm- loud but could be tolerable for some. 1200rpm loud as my Noctua NF P14s and my NF F12 at full (Silverstone pushes a lot more air but Noctuas sound nicer). At 1500 it is loud but not as loud as my Scythe Ultra Kaze 2000rpm at full.
1500-2000rpm- very loud, louder than my Kaze. (My GPU fan is however still the loudest component at full)
At 2000rpm vs the Kaze and the Silverstone, the Silverstone pushes far more air and the force feels a lot stronger.
I recorded this with a crappy iphone approximately 50cm away with the fans outside, hopefully this will give you an idea (the phone makes both fans sound louder though)
Ultra Kaze 2000rpm
Silverstone FHP 141 2000rpm
http://picosong.com/RCyM/Edited by Wumbologist - 6/29/13 at 3:33pm