VOC sound effects are the wave sound effects used by the Xeen games, the other being the .M music format.
The VOC files are, for the most part, standard Creative Voice files.
VOC files store digitized wave sounds, including the speech used in cutscenes and monster sound effects. This does not include the NPC speech used in the World of Xeen CD version - this is stored in CD audio tracks.
File Format Edit
VOC files can always be recognized by an identifier string at the beginning of the file: "Creative Voice File" followed by the byte 0x1A. Some Xeen VOC resources instead begin with "BullShit Voice File", again followed by the byte 0x1A. This obviously does not follow the Creative standard, but the Xeen engine does not check this identifier string at all. The exact purpose of this alternate identifier is unknown.
The remainder of the VOC file format is already extensively documented (see the external links section below).
It is extremely easy to convert a valid VOC file in to a standard WAV file, which may be the easiest way to play these resources depending on what kind of audio formats the development platform supports.
VOC format is not a commonly used format, and most popular players like Windows Media Player, QuickTime, iTunes, etc and devices like iPod, iPhone, iPad, Zune, etc do not support this format.