Sound issue (not smooth)

I couldn't find anything related to this (as it's also not easy to find the right keywords)...... so forgive me if this has been discussed before.Anyhow.... I'm currently having some issues with the smoothness of the sound during engine spool-ups. Everything else sounds fine, but the spool-up sounds like it is skipping steps as if it was lagging heavily, but the sim isn't lagging at all. I'm currently reinstalling Flightsim with all it's Add-Ons.... I never had this before and it sounds like it's just the 3rd party sounds. Perhaps I'm still missing a file.... it's just I have no idea where to start at to fix this issue. Hardware seems fine..... the only stuff I've installed until now are AI, 3-4 aircraft, a few sceneries, FSUIPC and the 9.1 update.Regards,Amadeo