Strange noise coming from case only with specific game

Now this noise starts coming from my computer when The Sims 3 is maximized, and goes away when I minimize it. It's not very loud but it got me worried. It's most intense during the intro cinematic and barely audible afterwards. It's a strange high-pitched noise, I'd consider it coil whine but it doesn't happen with anything else. Staring at the Windows desktop, stressing my hardware with synthetic tests, playing extremely intensive games, NOTHING else produces this noise. Anyone have any idea what it could be?
 
It seems it's coming from the back of the case, and this is in line with what I just discovered. It seems directly proportional to GPU usage. Apparently the devs of Sims 3 didn't realise there's no display that can output over a thousand frames per second and didn't cap the engine. The result being that unless I force it to use Vsync via AMD's Radeon Settings it will literally max out the GPU even at the menu and push out about 1300FPS. Once I force Vsync, GPU usage goes way down and the noise becomes practically inaudible (it's still pretty quiet even when it's "loud" but it just got me worried).

This is still pretty weird as the GPU doesn't make any such noise even when being hammered by games like Darksiders, Fallout 4, War Thunder etc.