My PC plays a weird sound whenever I stand up from the desk (opens in new tab)

Electrostatic discharges from chairs can interfere with USB and display signals:

"Surprisingly, we have also seen this issue connected to gas lift office chairs. When people stand or sit on gas lift chairs, they can generate an EMI spike which is picked up on the video cables, causing a loss of sync. If you have users complaining about displays randomly flickering it could actually be connected to people sitting on gas lift chairs. Again swapping video cables, especially for ones with magnetic ferrite ring on the cable, can eliminate this problem."

https://support.displaylink.com/knowledgebase/articles/73861...

Demonstration:

https://www.youtube.com/watch?v=voW5kEI7JKE

A paper about this phenomenon, titled "A New Type of Furniture ESD and Its Implications":

https://emcesd.com/pdf/eos93.pdf

The top comment says it's the system sound for inserting/removing a USB storage device. I'm guessing it's a loose connector or shorted wire and the vibration from standing up and moving the chair is causing it to briefly disconnect.

In such cases I suggest to install some sort of accelerometer near computer, best something like arduino with sensor, may be possible to use smartphone with app, and monitor accelerations and try to make correlation of acceleration, sound and computer logs (sure better if switch to debug level).

I have lot times seen issues, when in concrete building, sit/stand causes vibration, which temporary turned off ground contact of some device and some strange unwanted things happens.

The most annoying in my life, where restarting of hdd drive. At beginning I thought, it caused because drive is broken. But than I checked connections and found just weak molex ata power connector - than i just use pliers to slightly bend contacts and those effects disappear forever.