Hovercontrol will soon be upgrading the multiplayer voice server from Teamspeak 2 to Teamspeak 3. In order for you to use the new server you will need to install the Teamspeak 3 client.
The Teamspeak 3 client software can be found here:
Teamspeak 3 Downloads
You will be able to have both your Teamspeak 2 and Teamspeak 3 clients installed, in case you still need to use other servers that are still Teamspeak 2.
We will have further announcements, but for now, the important thing is to get your client software installed