an interesting bug with propeller sound

[raduz]

hi everyone,

I discovered something strange: the turn count you hear via hydrophone is supposed to be identic with the real turn count of the ships propeller. so I made a mission with only one C2 and I adjusted its max RPM in the .sim file to 25. then I used external view to count visually the turn count. it was 25, indeed. then I checked the hydrophone and it was 25.

but then I set the max RPM to 15. the real turn count was 15, all right, I was able to count visually the revs. but when I checked the hydrophone, I heard 21 RPMs! anytime I set the max RPM to <22, I always heard 21 RPMs, no matter how slow turned the propeller. I even set the RPM to 1, and the propeller did 1 turn per minute, but the hydrophone was telling me 21 rpms! the same goes for max. RPM. it is 47. you can hear max. 47 beats per minute although the propeller turns much faster.

I tried to modify the propeler_4_hyd in the sounds (I made it faster in the audacity software) but this just pushed the RPMs up and that was it (the limits were no more 21 to 47 but rather 42 and 94).

do you have any idea where this can me modified or whats the reason of this issue?
I checked the sh3.sdl file (propeller_4_hyd used by C2) but I didnt find anything interesting (there is just loop, volume, pitch, doppler factor, max and min radius).