This is an updated version from the original post Enemy Territory on Ubuntu 12.04 with sound. Below are my notes on having sound running correctly on Linux Mint 17. Assumptions:

Sound in Enemy Territory

Some smart cookie (http://nullkey.kapsi.fi/et-sdl-sound/) has written a SDL wrapper for Enemy Territory pushing the audio through SDL in place of the default OSS/system PulseAudio.  

Download the wrapper

$ wget -q -O - http://nullkey.kapsi.fi/et-sdl-sound/et-sdl-sound.gz | gzip -d > et-sdl-sound && chmod a+x et-sdl-sound
The above command line will download and unpack the et-sdl-sound script.  

Locate libSDL

For the next part you will need to know the location of the game installation (if not default) and the location of your 32bit libSDL.so To find your 32bit libSDL:
$ locate libSDL
My 32bit library was located at /usr/lib/i386-linux-gnu/libSDL-1.2.so.0  

Edit the script

$ nano et-sdl-sound
Uncomment the LIBSDL line and edit it to include the location of your 32bit libSDL library
LIBSDL="/usr/lib/i386-linux-gnu/libSDL-1.2.so.0"
Save the file and execute the game with using the et-sdl-sound script in place of the standard executable
$ ./et-sdl-sound

Done

That's it, Enemy Territory fired up with sound after the steps above were completed

=======older method============

Enemy Territory sound is a fickle thing, at least on my system. Below are my notes on having sound running correctly on Ubuntu 12.04. Assumptions:

Sound in Enemy Territory

Some smart cookie (http://nullkey.kapsi.fi/et-sdl-sound/) has written a SDL wrapper for Enemy Territory pushing the audio through SDL in place of the default OSS/system PulseAudio.  

Download the wrapper

$ wget -q -O - http://nullkey.kapsi.fi/et-sdl-sound/et-sdl-sound.gz | gzip -d > et-sdl-sound && chmod a+x et-sdl-sound
The above command line will download and unpack the et-sdl-sound script.  

Locate libSDL

For the next part you will need to know the location of the game installation (if not default) and the location of your 32bit libSDL.so To find your 32bit libSDL:
$ locate libSDL
My 32bit library was located at /usr/lib/i386-linux-gnu/libSDL-1.2.so.0  

Edit the script

$ nano et-sdl-sound
Uncomment the GAME_PATH line and edit to your installation path
GAME_PATH="$HOME/et/"
Uncomment the LIBSDL line and edit it to include the location of your 32bit libSDL library
LIBSDL="/usr/lib/i386-linux-gnu/libSDL-1.2.so.0"
Edit TMP_DIR from the default, my installation will not preload from /tmp this was the kicker and had me stumped for a while. As soon as the was changed to the installation directory it fired up with sound.
TMP_DIR="."
Save the file and execute the game with using the et-sdl-sound script in place of the standard executable
$ ./et-sdl-sound

Done

That's it, Enemy Territory fired up with sound after the steps above were completed