Different engine sounds for AI Traffic

Just discovered a way to make FSX use different engine sounds according to the engine variation of an aircraft keeping them in the same folder. Just as it is done for user aircraft sounds: sound.xxit can simillarly be done soundai.xx by adding soundai=xx in aircraft.cfg. Also if you want ai aircraft to sound like the realistic user aircraft sounds downloaded from the net, copy paste the sound.cfg from sound.xx to soundai.xx folder and rename it soundai.cfg, in it replace all 'filename=' by 'filename=..sound.xx' and that's it!Any one knows how to make the sounds roar when looking at the aircraft from behind and whine from front in outside view?