ai sounds eating framerates!

Few days back I manualy added around 35 airlines to my traffic and aliased all the airplanes to 738 soundai. Expecting to have a nice plane spotting view I ran a flight with an invisible model. Every thing seemed ok until after a few minutes when 4-5 planes became active in my vicinity. Their engines started rumbling with sound files set for full throttle playback in the soundai.cfg, sounding really silly while taxiing or holding short. A little later as more aircraft become active, fps started decreasing from 25 to below 10 and then suddenly 1fps! my system virtually hanged until I pressed Q in desperation. With sounds off, the fps jumped back to 25fps smooth. Moving away by about 5nm from the airport also allowed sim to run normal. Now ofcourse I am forced to fly with sound_lod=1 in fsx.cfg with fs9 type ai sounds.I have the latest xp x64 sound drivers installed for my hardware.Is the fsx ai sound bound to hit performance that severe or am I missing something?that no threads are relating such problem has made me hopeful..