No HDMI sound using Mini DisplayPort or Thunderbolt

Problem

You are unable to get any sound via your HDMI connection to your Mac when using a Mini DisplayPort or Thunderbolt adapter. This may have occurred after upgrading to the Lion operating system.

Solution

• Check the device is selected as it may not work automatically:
1. Click the Apple icon in the top left of the screen.
2. Click System Preferences.
3. Click the Sound icon.
4. Click the Output tab.
5. Click on the correct device.
• Reset the PRAM
• Reset the System Management Controller (SMC)