Since I upgraded to Windows 8, audio is not working in Skype. I’m using the Skype program, rather than the Windows Store App and found that the audio settings were wrong.
By default, Skype had selected some sort of virtual speakers (perhaps internal speaker?) or alternative audio output, rather than my external speakers and this was causing the audio to not be working in Skype, but work in other programs.
To fix the audio problem, I launched Skype, clicked Tools -> Options -> Audio Settings and selected the correct speakers from the drop down arrow. I used the green play button to prove that the audio was working once I’d selected the correct speakers.
Other issues that may cause this problem for other Skype users could be:
Your speakers are physically turned down, turned off or broken
Your speakers are muted or turned down in Windows 8