Motherboard Fan
Motherboard Fan
Check your system settings or BIOS to turn off the motherboard fan. If unsure, consult your hardware manual or a tech support source.
Remove the heatsink and fan, then install a replacement fan. You might need to attach it with tape to the chipset heatsink. It won’t look great, but it should be quieter.
I adjusted it to silent mode, but the annoying buzzing persists.