I could help with that.
Truck_Description_File#Soundsources2
All you have to do is change the soundsources tag to soundsources2
then inbetween the node number the sound comes from and the actuall sound put a
-2, for the sound to be there all the time in any camera
-1, for external camera only
And anything bigger then a 0 for sounds inside the cab only.
Heres the ones from my jeep. They are all sounds that work at any camera view.
soundsources2
14, -2, JeepWranglerUnlimited-Engine
11, -2, JeepWranglerUnlimited-Starter
110, -2, JeepWranglerUnlimited-Horn
57, -2, JeepWranglerUnlimited-Parking
22, -2, JeepWranglerUnlimited-Exhaust
49, -2, JeepWranglerUnlimited-Shift
If you need any help let me know.