Sound problem: Flyby 'pitch' is reversed!

After downloading and installing a couple of planes, I have encounter a small but frustrating problem. it seems that the 'pitch' of the sound in the 'flyby' view is reversed! When the plane is aproaching, the pitch should be high, but it is low. When the plane passes by the camera, it should sound low, but it is higher! Any suggestions on how to fix this?