Just to confirm, I am having the same exact issue with sounds as Flavio described, although I don't seem to have access to download the v4 compatible installer. I purchased the Bronco X in 2012 from pcaviator.com and my download links are now dead. But, I was able to install by copying the prepar3d.exe and renaming to fsx.exe, running the original install, followed by the 112 service pack and hot fix. In the meantime, I also tried aliasing sound in the other Garrett turboprop aircraft that I own, the Aerosoft Twin Otter Extended, but no joy.
FWIW, the Aerosoft Bronco is my absolute favorite VR aircraft with that spectacular view out of the cockpit and snappy handling. Low level exploration is fantastic. The 3D pit is really wonderful in this aircraft in VR, considering it was created when it was. Long live the Bronco X!