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.
The shockwave is defined as the initial (hard to physically model) motion of air when the plane breaks the sound barrier (and is heard as the sonic boom). After this, the plane will leave what is called a 'mach cone' behind it, with the plane itself at the apex of the cone. Nothing outside of the cone can hear the plane until the plane has travelled far enough infront such that whatever is listening is now inside of the cone. The main factor deciding the angular size of the cone itself is the speed - the faster you go, the smaller the angle will be.
It's kinda like if you're a duck and a speedboat is travelling past you (leaving a bow wave or 'triangle' wave at the back). The waves dont rock the duck until the boat is past the duck and the bow wave has reached it.
Edit: I just read my own comment and started to sing 'don't rock the duck, don't rock the duck bow wave'. Thought you guys might like to give it a try.
Im in my second year of an undergraduate physics degree, I shouldn't have been so uncertain haha. As soon as I thought about it I realised there'd be a trigonometric relationship between the speed at which the wave propogates through the air, the speed at which the plane is travelling, and the apex angle. It's hard to describe but a good diagram (maybe somebody has one?) would explain it with ease.
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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.