Finished my current build a week ago, everything was going fine. Then, last night, I heard a weird sound coming from my case that I haven't heard since the build was done. The best way I could describe the sound is a slight whistle-like sound winding down. The sound only happens maybe once every 2-3 hours and only started recently (over a week since the build was completed). My guess is that it's the sound of a failing PSU, but I would appreciate a second opinion.
Case: Corsair 650D
MOBO: ASRock Z77 Extreme4
GPU: GIGABYTE Radeon HD 7970 3GB
CPU: Intel Core i5-3570K
CPU Cooler: Thermaltake Frio
RAM: G.Skill Ripjaws X Series 8GB (2 x 4GB) 2133
SSD: Samsung 830 256GB
HDD: Seagate Spinpoint F3 500GB
PSU: Corsair HX650 650W
I realize that identifying problems based on sound descriptions is a bit tough but anyone have any guesses on what it could be? If all else fails, I'll just sit by the case with an empty paper towel tube and try to pinpoint the location of the sound but anything that could save time and the hassle of waiting for a sound that comes only once every 2-3 hours for 1-2 seconds would be a huge help.