Since you are playing it to everybody, I would use
PHP Code:
client_cmd(0, "mp3 sound file")
. If you have a WAV file, you can convert it into MP3 format file. This is a converter,
Convert WAV to MP3
Good thing is MP3 is smaller than WAV with very little quality changes.
EDIT: Btw if you have a CVar remember to use
return PLUGIN_HANDLED instead of
return to prevent run time error 4.