5 of my corsair psu's did that, it didn't bother me that much though.
I had TX750 (didn't whine), TX750V2(whine), HX650(whine), 2x HX850( both whine) now a HX1000(whine).
On the other hand, my other "lower-end" OCZ modxstream PSUs never whined and neither did my Antec Truepower New 750 and...