$ sudo apt-get update
$ sudo apt-get install mbrola-de6 

mbrola-de6 is installed in your system.

Make ensure the mbrola-de6 package were installed using the commands given below,

$ sudo dpkg-query -l | grep mbrola-de6 *

You will get with mbrola-de6 package name, version, architecture and description in a table

mbrola-de6 package basic information: