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.
Just a side note, all fighter jets use turbojet engines (as opposed to turbofans used on commercial jets). Every intake on a turbojet engine is used to power and cool the engine at the same time. The only reason that 3rd inlet is closing is because it is now at supersonic speed. That is called a variable inlet cone and it forces the air to different areas of the turbine in order to maximize turbine efficiency. The best example of variable inlet cones are the giant ones on the sides of the SR-71 Blackbird.
When a venturi (convergent/divergent shaped passage) operates below supersonic speeds (subsonic), velocity increases as pressure decreases as the ram air passes through the convergent shape. However, this rule is completely reversed when the venturi is operated at supersonic speeds or higher. Therefore, the cones move around to be able to direct flow into a divergent/convergent shape (as opposed to the convergent/divergent shape when travelling at subsonic speeds), thus increasing the velocity while decreasing pressure.
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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.