First, Get a tool to browse MPQ files with. i suggest Ladik's MPQ editor. (google it)
then open up the editor and open the Sound.MPQ file (its usually located inside of C:\program files\World of Warcraft\data)
the voidwalker sounds should be located in Sound>
Creature>
Voidwalkerright click on the files you want to use and click extract, then do said thing and place the files wherever you feel like.
i hope this helped.
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