Originally Posted by
Jagboi
They are attached to the plane, just the same as you are; and you're both moving together with a relative speed compared to each other of zero. The sound generated by the engine radiates outward at the speed of sound and thus you hear it.
Small point of pedantry, but wouldn't the sound
radiated by the engines be in the foward-rear plane, i.e. the direction that the energy is being released (backwards)? The noise from inside the plane is conducted to the skin of the aircraft by kinetic energy and subsequently radiated from the solid of the skin into the cabin?
(I agree with your intertial reference frame stuff, by the way)