Hello!
Well, thats kind of a funny bug: A few times a player with a E-Jetpack came next to me and suddenly I had Jetpack sound myself when I was jumping without a jetpack!
Also, when I put on my own Jetpack at that moment I suddenly had no jump or jetpack sounds at all!
This was also reported by other players on our server before but those lazy bastards refused to help me to find out a way to reproduce the bug (ok, it was 3am, granted...)
Maybe somebody else found out how to reproduce that bug or if it happens with the normal Jetpack, too?