Do you perhaps have the Staggerwing or one of the other Carenado ‘famous flyers’ installed?
If yes; did there happen to be another player in your vicinity flying that plane?
There’s currently a really annoying multiplayer sound bug with those planes, where the sound of that other plane originates in your cockpit as well, drowning out your own engine noise. Seems to be an issue with many Carenado developed planes.