Hi,
It looks like this may well be a hardware issue.
As a further test, try the following.
1. Create a bootable Ubuntu CD - a guide on creating an Ubuntu CD and the download can be found Here.
2. When created, follow the guide on the link below to Try Ubuntu.
http://www.ubuntu.com/download/help/try-ubuntu-before-you-install
The 'Try Ubuntu' option runs the OS from the CD without the need to install on your HDD. This will be slow than normal when running from a CD, but see if you have audio through the speakers.
Regards,
DP-K