[[XST]O_x]

I don't think there is a sound for fart in the game.
But why not use PlayAudioStreamForPlayer?

pawn Код:

CMD:fart(playerid, params[])
{
    new Float: pX, Float: pY, Float: pZ;
    GetPlayerPos(playerid, pX, pY, pZ);
    PlayAudioStreamForPlayer(playerid, "http://www.soundjay.com/human/fart-01.mp3", pX, pY, pZ, 6.5, 1);
    SendClientMessage(playerid, -1, "Eww");
    return 1;
}