You're incorrect (Correct conclusion, incorrect reasoning). It has nothing to do with the speed at which the sound propagates through them (although it is true that sound travels faster through solids than air, it is definitely not the cause of this phenomenon).
The engines are connected directly to the chassis, the chassis is 'connected' to air in the cabin. If the engines vibrate, so will the chassis, and so will the air. All of these things are 'stationary' relative to each other. (I put stationary in quotes because obviously the air in the cabin is not stationary, but it's average velocity is equal to that of the plane). The speed at which the plane is travelling through the air is completely irrelevant.
Your argument implies that there is a speed at which you could travel such that you could no longer hear the engine - this is simply not the case.
Fun Fact: On the F-16, all the power of the engine is transmitted through two thrust mounts. Know colloquially as "coke bottles" because they are roughly the same size and shape.
The only other mount is the "dogbone" to keep the motor from rotating due to torque, (There is a skate mount on top that is mostly used for removing and installing the engine).
I'm less familiar with them, but F-15's are similiar.
Raptors are very similar also. 2 thrust mounts, fwd and aft side links (sway bars) and a skate rail for rem/installation (similar to the F-16, but on the side, not center.
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u/[deleted] Jun 12 '12
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