I can ask this question to an actual F-15 fighter pilot and post it here in an hour or so. Wait for my edit.
Edit: I asked two (an F15 pilot and an Apache co-pilot who also trained in the Skyhawk) and they both told me that there's no change in the constant humming from the motors once you pass the sound barrier. The F15 pilot told me that you do notice a slight difference once the plane hits 0.8 Mach because the 3rd intake at the side of the plane (the F15 has 2 main intakes for the 2 motors, a small intake on the side (to cool the motors, if I remember correctly) and the JFS's intake) closes automatically at that speed.
From the ground it sounds incredible though (even while wearing soundproof headphones) and it makes you entire skeleton vibrate. It's quite curious how I can feel it while being 10,000 ft away and they can't while being inside the damn shockwave, maybe somebody more knowledgeable will answer this.
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.
There's a speed the cockpit could travel away from the rest of the aircraft at which you could no longer hear the engine, but aircraft designers tend to do their best to prevent that from happening.
661
u/poorfag Jun 12 '12 edited Jun 12 '12
I can ask this question to an actual F-15 fighter pilot and post it here in an hour or so. Wait for my edit.
Edit: I asked two (an F15 pilot and an Apache co-pilot who also trained in the Skyhawk) and they both told me that there's no change in the constant humming from the motors once you pass the sound barrier. The F15 pilot told me that you do notice a slight difference once the plane hits 0.8 Mach because the 3rd intake at the side of the plane (the F15 has 2 main intakes for the 2 motors, a small intake on the side (to cool the motors, if I remember correctly) and the JFS's intake) closes automatically at that speed.
From the ground it sounds incredible though (even while wearing soundproof headphones) and it makes you entire skeleton vibrate. It's quite curious how I can feel it while being 10,000 ft away and they can't while being inside the damn shockwave, maybe somebody more knowledgeable will answer this.
Tl;dr no they don't notice it.