I am sorry you are having this problem with your system but let me help you.
We have received reports from other customers that are having problems with the Audio through HDMI connection but we have found the solution for this.
Please note that it is necessary to update the graphics driver to the latest. You can download the latest driver at the following link:
It is also important to install the latest BIOS update for the system. We have been told by customers that they had to request the BIOS update to the Computer Manufacture because the one that fixes the problem is not available to download.