I wondered  why my frame rates were suddenly dropping when all was ok before.  So I set the fps to unlimited and experimented, flying normally with any aircraft or any sound file the fps was around 50 with sound off, popups made little to no difference exterior views a small drop, turned on the sound and the frame rate dropped to around 5fps.I have no sound card but the onboard one,it does not matter much to me as my hearing is bad after 20 years working on a/c  before ear defenders wre even thought of .Is there anything I can do to increase the fps other than turning of the sound altogether, that does make it difficult to talk to atc.