@Frazzlee
the turbines sounds for sure... sucking the air in front of them (;
the air passing over the fuselage... this one has to be heard after a certain speed has been reached... subsonic for sure... definitely subsonic
and then just before reaching but not after passing the 1225 kph barier a very loud, almost defining sonic boom ((:
and after 1226... i repeat 1226kph... 6 not 5... complete and utter silence
now i know this is just like a plane but the vehicle ingame has to be exactly that... classified as a plane with no wings that never flies / takes off , and has big mofo turbines
just to make an idea about how the air friction on the fuselage sound like when almost reaching sonic speeds, look at this :
time 0:10 seconds (i have heard irl something like that and can confirm that is the sound of air trying to get out of the way of plane, you can hear the plane only after it pases you, you can't hear it closing in cause of the speeds)
about sonic booms... about the same, you can't hear it until plane passes you, if speeds over sound speed and it is constant after if speeds remain over 1225 (:<
best example is this
For the driver is diferent story: he can hear everything until the sonic limit is reached, so that means that he can't hear the sonic boom hapening or anyhing after that ! sorry for my bad spelling, english is not my native language (;