I Get a similar 3D Sound effect with the following
volume =100-distance#=getDistance(obj1,obj2)+40
if GetSoundInstancePlaying(mySoundInst)
SetSoundInstanceVolume (mySoundInst,volume)
endif
function getDistance(objectID as integer,objectID2 as integer)
distance as float
vec1 as integer
vec2 as integer
vec1=CreateVector3(GetObjectWorldX(objectID),GetObjectWorldY(objectID),GetObjectWorldZ(objectID))
vec2=CreateVector3(GetObjectWorldX(objectID2),GetObjectWorldY(objectID2),GetObjectWorldZ(objectID2))
distance=GetVector3Distance(vec1,vec2 )
DeleteVector3(vec1)
DeleteVector3(vec2)
endfunction distance