OK i just got two power supplys and 2 news video cards they are each by BFG 550 watt power supply and both Nvidia 9600GT OC. I put one of each in my tower and it seems to work fine minimal noise and working great. However in my wifes computer theres this high pitch whistle noise...and its killing me. I made sure that theres plenty of airflow and no wires are blocking any fans. I think the sound is coming from the video card but it could be just a little bit above at the PSU. Im not really sure what her motherboard specs are exactly all she has was a store bought emachine W5243 (i checked their homepage for some reason just that one doesent seem to want to load)
The whistling is likely to be the capacitors on your 9600. All caps make a sound of sorts, the ones nVidia uses seem to be louder than most! google search for whistling video card/hissing nvidia etc and you'll see a multitude of posts...
There doen't seem to be any perticular reason why some are very audiable. I'm sure it is down to electro magnetic resonence or some such which is beyond my wine addled mind
I had an 88000GTS which alternated between sounding like a song bird and a hissing snake in intensive apps/games
I had the same problem, and the guy from service told me that the strong sound only appears if the card doesn’t get enough power from the PSU. In one of my computers I get a sound only when I put the video card in the motherboard for the first time, after 10 startups the sound disappears. Change you’re PSU if possible.