Turn off the hdmi sound card of the motherboard BIOS.
The motherboard has two sound cards, one is a common Realtek Rayyu 665 sound card, and another is an HDMI sound card. The HDMI sound card can be turned off in the motherboard BIOS. My Onda A78GT has this option,
Or if you reinstall the HDMI driver and don't know what chipset you are, you can search the driver corresponding to your chip online: NVIDIA nForce HDMI Audio Audio Card Driver ATI HDMI Audio Driver