What is mumble ? 

Mumble is an (VOIP) “Voice over ip ” application primarily designed for use by gamers

Mumble uses a client-server architecture which allows users to talk to each other via the same server. it has a very simple administrative interface and features high sound quality and low latency.All communication is encrypted to ensure user privacy 

Mumble is free and open-source software, is cross-platform, and is released under the terms of new BSD license.

Original author                  :   Thorvald Natviq
Written in                           :   C++
Operating system supports :   Linux , Mac OS X  , Microsoft Windows ,iOS,           Android 
Platform :Qt
Type       : VoIP  Client and server 
License   : New BSD license 
Website  : http://mumble.sourceforge.net/   and http://www.mumble.com/

 Ubuntu / Linux mint

* Note that for the mumble-server package on Debian or Debian-based distributions, you should not start the server manually. After you install and configure it, it will start on its own.

 
Ubuntu carries whatever Mumble version was current at the time of the release in the universe repository. Mumble team also maintain a PPA that has the latest version for recent Ubuntu versions(Linux Mint is based on Ubuntu)

 sudo add-apt-repository ppa:slicer

it will ask you permission so enter your root password , then press enter key

 sudo apt-get update

paste above terminal commands to update 

 sudo apt-get install mumble

paste above terminal commands to install mumble 
it will ask you for permission 

type 

  y 

then press  enter key

its installed now 

 sudo apt-get install mumble-server

 sudo dpkg-reconfigure mumble-server