I tried that. Turning World audio to 0% and the jet is still just as loud as ever.
Both in 1.5 and 2.0
ETA: I just figured it out... Literally if I make a change to the audio then exit DCS, then restart it, my audio has changed. Sheesh.
Apache600 thanks for the response. I think I should report this as a bug. Gonna play with it a bit more before I do.