Hello again j_dext,
Thank you for responding to my post requesting additional information. I am going to get you to recover the original audio drivers that came with your computer to ensure this is not a drivers issue. To do this I would like you to review and follow the instructions in the HP Support document: Using Recovery Manager to Restore Software and Drivers (Windows 8). I understand that you are running Windows 8.1, but I believe that this should resolve your audio issue if it software related.
Please re-post with the results of this step. Thank you for posting on the HP Forums. Have a great day!