Some PCIe GPU fans spin uncontrollably on macOS computers, and it is very annoying to hear these fans’ buzzing. My computer is built with a Radeon RX 570 and sometimes has the above fan issue, especially after booting.

I searched the internet and found a tricky solution (source) that to install a benchmark software called LuxMark. After opening this software and running for a few seconds, the graphics card fan will magically return to the normal speed.