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Author Topic: Sound....at the speed of sound ?  (Read 4704 times)

Offline neilep

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Sound....at the speed of sound ?
« on: 29/04/2006 00:49:28 »
Hi All,

I was wondering, whilst watching a program about aircraft carriers !! (Gosh !!..do I know how to live it up on a Friday night or what ? :()...which was actually very interetsing..really.

...anyway....If I was strapped on the outside of a plane that increased it's speed to over and above the speed of sound, before passing out or retiring from life, would I be able to hear anything ?..what about my own last words ?

I know this there is no problem when inside the plane...but on the outside ?

Thanks



Men are the same as women, just inside out !


 

another_someone

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Re: Sound....at the speed of sound ?
« Reply #1 on: 29/04/2006 01:16:34 »
The sound of air rushing past your ears would probably drown out everything else.

But besides that, there would be two other factors.

Firstly, the speed of sound through solids (such as the metal of the aircraft body, or human bone) is faster than the speed of sound in air so sound could still be conducted to your ear through your bones.

Secondly, if you are behind the supersonic shock wave, then the air you are in is actually subsonic (but it does depend upon whether someone stuck your head out beyond the shock wave, or if you are nicely tucked behind the shock wave).

Ofcourse, if your hard is stuck out beyond the shock wave, then the contours of your body would create there own sonic shock waves, which probably would not do a great deal to maintain the integrity of your body.

Even if you were behind the shock wave, the complex contours of your body could well create local airflows that are supersonic, and thus create mini shock waves.

Lastly, sound aside, the friction of the air on your body could easily heat it above the boiling point of water.



George
« Last Edit: 29/04/2006 01:20:55 by another_someone »
 

Offline neilep

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Re: Sound....at the speed of sound ?
« Reply #2 on: 29/04/2006 01:30:53 »
Thank you George,

So, assuming there is no sound of rushing air past my ears I would not be able to hear my own speech....or screaming for that matter !

What about a sensitive microphone attached to the plane George ? it's ahead of the shockwave and is travelling at supersonic speeds. I presume,it would not sense any sound at all. Would that be right ?

Thank you.

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another_someone

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Re: Sound....at the speed of sound ?
« Reply #3 on: 29/04/2006 03:07:03 »
quote:
Originally posted by neilep
So, assuming there is no sound of rushing air past my ears I would not be able to hear my own speech....or screaming for that matter !



You wouldn't be in any fit state to make a scream but you would probably still feel the vibration of the jet engines through the body of the aircraft.

quote:

What about a sensitive microphone attached to the plane George ? it's ahead of the shockwave and is travelling at supersonic speeds. I presume,it would not sense any sound at all. Would that be right


Firstly, you would still hear sound from infront of the aircraft, just you would not hear sound from behind it (you may have to take account of some serious Doppler shifting).

Secondly, if the microphone is not isolate from the aircraft body, it will still hear sounds coming through the body of the aircraft, since the speed of sound through metal is much faster than the speed of sound through air, and so can travel forward even as the aircraft travels at speed faster than sound in air.



George
 

Offline daveshorts

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Re: Sound....at the speed of sound ?
« Reply #4 on: 30/04/2006 11:27:39 »
The microphone would in theory be able to hear sounds coming from in front of the plane, but not behind it. The sounds from in front would be immensely doppler shifted as you are moving very fast, and very distorted as in a shock wave air will stop behaving in a linear way ( this means that if you have 2 sounds waves with amplitude 1Pa if they are added together the total is no longer an amplidude of 2Pa - this does all sorts of strange things to how sound propagates). Also the bufferting the microphone would receive from the shockwave which in itself is sound, would probably be thousands if not millions of times stronger than the sounds you are trying to listen to.
 

Offline neilep

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Re: Sound....at the speed of sound ?
« Reply #5 on: 30/04/2006 14:22:35 »
Thank You Dave and Thank you George.

I consider this question answerd.

So, should I be in the location where there is no sound, no buffeting, all possible causes of extraneous sounds defeated, including the ability to hear ones own internal organs...then I would experience the ultimate silence....perhaps like being inside a vacuum ?..and yet if able to remain conscious and function normally I would be whizzing along at above the speed of sound......cheers.

Cheers


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Re: Sound....at the speed of sound ?
« Reply #5 on: 30/04/2006 14:22:35 »

 

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