HD Audio Background Process is the Realtek's ravbg64.exe file and it is located in the C:\Program Files\Realtek\Audio\HDA folder.

If your HD Audio Background Process is using high CPU or resources, open Devices Manager and expand the Sound, Video & Game Controllers category.

Here right-click on Realtek Audio Driver and select Update.

Else you may reinstall this audio driver. You have to Uninstall this driver, restart your computer and then Scan for hardware changes and install the freshly offered audio driver.

If this process is located anywhere else, it could be malware - so scan your PC with your antivirus software, in this case.