I have added to the SVN the skeleton of 3d sound support (not working at all, a probe of concept).
It will use OgreAL that uses OpenAL internally and Gazebo will be able to be compiled without it (by default).

I am not sure about the API (how to manage clients recording audio???), if you can take a look to the changes of revison 276, I am sure you will find flaws.

Comments/suggestions will be welcomed.

Jordi Polo Carres
NLP laboratory - NAIST