How do I use Microsoft LiveChat LX-3000?

Install pavucontrol. You should be able to get it working with that.

Found an english source along with the german one I posted in comment.

so I had the problem of not hearing the sound through my Microsoft LifeChat LX-3000 which was connected to my laptop with sysop Ubuntu 14.04 LTS. I tried these two easy steps and it worked out for me.

1. Installing pavucontrol by running the following command line in the Terminal:

   sudo apt-get install pulseaudio pavucontrol padevchooser
   

2. go to system setting,

3. find item SOUND (in my laptop, sound was between printers and wacom tablet),
4. in the OUTPUT section, switch the Speakers from Built-in-Audio to Microsoft LifeChat LX-3000