Post Scriptum

Firstly the speed of sound in airplane grade aluminum is "slightly" higher than in thin air, an order of magnitude would be my initial guess. So you are correct that any vibration or whatever from the engines will definately transferred to the whole fuselage. The actual "engine noise" is then another issue.

Secondly, it is not only the engine that you are hearing, also the "wind shear" against the whole fuselage creates audible sound...well, audible would be slight underestimate for the noise created in supersonic speeds.

When you drive on a highway with your car doing 100 km/h, barring you have V12 Ferrari, what are you actually hearing on a stable highway speed:
1. Noise from the tires
2. Noise of air rushing towards the windscreen

Then multiple this speed by 20 and imagine what happens to 2. So, whether you could hear the engine in normal highway speeds or not, the other elements create so much noise that it is not really relevant whether you could hear the engine noise or not as the intensity of the other sources of noise is significantly higher

But for the actual question, as the engines are travelling on a same pace as you, but the medium, where the sound would travel from the engines outside the fuselage to you sitting inside in the front, only allows speed of sound, i.e., less than your travelling speed. So, in principle you would not be able to hear the noise from the engine if, in some idealized world there would be only "free moving air" between you and the engines. edit: specified this sentence.
Howcome my message is #1, have I changed my settings somehow...

Lee_Again

My son has justed asked me this little gem; and I can't think why the correct answer is correct.

Q - When travelling at or above the speed of sound you shouldn't be able to hear an object approaching. If that's the case, can you here a Concorde engine if sat towards the front?

A - lots of errs

In theory you shouldn't be able to hear them but I guess because they are structually connected and vibrations can travel 'forwards' is, I presume, part of the correct answer but if anybody can give a more scientific reasoning I'd appreciate it. I will, shamefully, take full credit with my son. Sorry.

Thank you,

Lee

angatol

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angatol

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cristo

Is your question can you hear concorde coming from on the ground, or can you hear concorde's engines while inside the plane?

I think you're asking the second question. The answer to this is the same as the answer to the question "if you're sat in concorde, will you be able to hear what the person behind you is saying?". Technically, all sound is vibrations, in materials or in air. Since you are in a pressurised box, the air in the plane is at rest, and so sound can travel through the air, in this case, the sound will travel through the fuselage from the engine and then through the air in the plane.

If the air in the plane wasn't at rest, say the exit doors suddenly opened, the air would then be supersonic and no, the people at the front of the plane would not be able to hear anything from behind them (though I suspect you'd have bigger problems than not having your drinks order being heard )

LiviLion

looks like the reply travelled faster than the OP. I've seen this on a couple of threads tonight.

Lee_Again

Maybe the question should be...

...If travelling at x mph can I answer a question before it has even been asked.

I think we've somehow developed time travel.

BizFlyin

This is a known vbulletin issue. It happens with this forum software.

Land-of-Miles

Concorde was much noisier at the back (and hotter) than it was at the front. The second cabin was thus unpopular with regular SSC passengers and in effect a pseudo J/Y effect prevailed between the forward and rear cabins.

Nicksta

One of the things I remember most vibrantly about flying R was the noise in the front of the plane. It was not the roar of engines, but instead the sound of rushing air. Imagine the worst windstorm you've ever head from inside a building and that's sort of how I remember the sound. I've read that it sounded like a 'sizzle', but I don't recall it that way.

Anyway, it does not answer the question pertaining to the engines, but for the records, it was moderately noisy.

Jagboi

This is a case of frames of reference. If you are on the ground and an object is approaching you at faster than the speed of sound you don't hear it approach because the object is approaching you faster than the sound it generates. The second reason is because there is the shockwave between you and the object, and the soundwaves don't cross over the shockwave.

In the case of sitting in the front cabin of Concorde, relative to you, the engines are not going faster than the speed of sound. 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.

Royce

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)

Jagboi

It probably is, yes. I expect there is engine intake noise too, that probably goes forward. I know the Olympus engines needed air to enter an subsonic velocities, but I don't know where/if there was a standing shockwave that would muffle the induction noise.

Like any plane though, the exhaust is louder and the rearmost seats will have more cabin noise than the front.

Zhivago

It's because this thread is Concorde-related!

binman

But without the price differential!

It was noises wherever you sat but wonderful non the less. My abiding memory was takeoff and the drop shortly after leaving the runway when engine power was reduced and afterburners turned off.

The whole experience was sublime and BA have not been the same company since it was taken out of service ( rightly) and vandalised by Eddington and Airbus ( outrageous)