Using links to voice NPC's without hakpack - possible? (override folder?)

Hey,
So as some of you may know I’m developing a language-learning PW - http://languagequesters.wixsite.com/lgqs

I want to add some voices to my NPC’s but I’d hate to make players use a hackpack. Can it be done using the override folder? Or some other way?
-Val

PS. This is for NWN:EE