Does this Mini DisplayPort to HDMI connector output audio?
The Original Apple-Adapter supports Audio for MacBook Pro and iMac Mid2010

From the Apple-Website:


  Note: *Audio support is only available for MacBook Pro 13/15/17-in.
  mid-2010 release; iMac 21.5/27-in. early-2010 release


Apple-Store Link

I've bought a cheap one from Belkin for my MacBook Air - but there is no Audio-Output!