You confuse me with this one.
You say you have the file downloaded, but then you say you use the package install command to download it?
Also, why on Earth are you using the .deb file for TeamSpeak3? You should be using the .run file which is what you download from their website.
cd ~; wget http://dl.4players.de/ts/releases/3.0.15/TeamSpeak3-Client-linux_amd64-3.0.15.run; chmod +x TeamSpeak3-Client-linux_amd64-3.0.15.run; ./TeamSpeak3-Client-linux_amd64-3.0.15.run