1. Run Steam VR.


2. Open the Steam VR settings


3. Select Audio, and change the audio output device to something other than INDEX HMD.


4. Open up Device Manager. Expand "Sound, video and game controllers." Uninstall "High Definition Audio Device."


5. From the main menu, select Action and "Scan for hardware changes." This will reinstall Index's sound drivers.


6. Back in the Steam VR audio setting select INDEX HMD.


You should now hear sound through your Index. For how long? I have no idea. This is a constant annoyance that I wish Valve would fix. But at least for now, it's a 5-10-second fix.