Worrying sounds from inside PC

[EvilGrins]

Whenever I'm idle or playing games, my fans seem to randomly emit a higher pitch and then sometimes it will go back to normal. I've taken off the side of the case while the PC is running but I can't really identify the culprit or see anything out of the ordinary. Is it normal for my fans to randomly sound louder even when I'm not using my PC? I can trigger the sound by launching a big game but it usually goes back to normal and then goes loud again. I don't have any dust build up either because the PC is still new. The fans just randomly seem to be more "worked" for a short duration, which happens completely randomly. Is this normal?

Another worrying thing I noticed is on my GTX 1080, one of the fans seem to be rotating faster than the other one when I'm not playing any games or watching videos. Is that normal...?

SPECS:
Processor (CPU): Intel® Core™i7 Quad Core Processor i7-7700k (4.2GHz) 8MB Cache
Motherboard: ASUS® ROG STRIX Z270E GAMING: LG1151, USB 3.1, SATA 6GB, Wi-Fi - RGB Ready!
Memory (RAM): 16GB Corsair VENGEANCE DDR4 3200MHz (2 x 8GB)
Graphics Card: 8GB NVIDIA GEFORCE GTX 1080 - DVI, HDMI, 3x DP - GeForce GTX VR Ready!
1st Hard Disk: 1TB SATA-III 3.5" HDD, 6GB/s, 7200RPM, 32MB CACHE
M.2 SSD Drive: 256GB SAMSUNG SM961 M.2, PCIe NVMe (up to 3100MB/R, 1400MB/W)
Power Supply: CORSAIR 650W CS SERIES™ MODULAR 80 PLUS® GOLD, ULTRA QUIET
Processor Cooling: Noctua NH-U14S Ultra Quiet Performance CPU Cooler
Extra Case Fans: 1x 120mm Black Case Fan (configured to extract from rear/roof)

 

[Oussebon]

It would be worth working out which of the fans - if it is a fan - is making the noise.

Holding a cardboard tube (e.g. kitchen roll tube) to your ear and the other end up to various fans can help. Or turning down the case fans if your case has a fan controller.

Bear in mind that even when a PC is idle, it's not always doing nothing. For instance, Windows things like the News app, the Film and TV app, even the calculator can sometimes run in the background even when you haven't used them, make use of GPU acceleration, cause your GPU to be at full clock speeds even though its load is practically zero, and run hot enough to have the fans come on. It won't be running very hot, so the fans can cool it below 60 (or whatever the threshold for 0db cooling is on Pascal) and switch off, then the fans not cooling means it starts to warm up again and hits the threshold where the fans come on again. I've seen my GTX 970 do this often enough.

I believe there are also some GPU models that can have asynchronous fan speeds since the fans are cooling contributing differently with respect to what parts of the GPU they cool, since different parts can run at different temps.

If in doubt, phone PCS and they'll be able to troubleshoot anything that needs troubleshooting and tell you if that's normal behaviour for what you own.