The way that sounds can be attached to effects in OpenOffice.org Impress under 
Linux is fairly complicated not because of the way sounds can be selected but 
because OOo does not use an existing working sound engine. There are mainly 
the ALSA and the OSS sound systems with ALSA replacing OSS as far as it seems. 
With actual distros you normally have a working sound system after install or 
upgrade. Why can't OOo use this instead of the Java installation you need to 
add. 
There is a workaround using the start process function but this does not 
accept parameters for the process so you need to setup a short shell script 
for each sound. I guess the easiest way would be to add a config parameter set 
where you can enter the pass to your preferred player and the start and stop 
commands needed to start a sound and stop it if requested. The only other 
parameter needed in the presentation would be the name of the sound file.