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Offline neilep

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Sound through a metal bar !
« on: 14/07/2006 15:31:09 »
Fellow Peeps Of Adroit Goodness & Gifted Skill.

Say, I had a long piece of metal, say cylindrical in shape with a circumference of 8 inches...maybe made out of stainless steel.

Now, if i was to hit one end..how fast does the sound/vibration travel along the path ?

Say, for instance it was a mile long !!..would someone at the other end still hear it [?] ...say it was millions of miles long and pointed into space and the last foot or so was maintained in an oxygen atmosphere...perhaps it's sticking through a space ships porthole or something !...would the sound reach [?]...is there a limit to how far the vibrations will travel [?]

Thank you for your kind consideration in this matter.... I shant start construction till I receive some confirmation, in the mean time I'm rubbing all my stainless steel pans with glass paper and am collecting the filings to melt down...I reckon a couple of pans should do it:)

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ROBERT

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Re: Sound through a metal bar !
« Reply #1 on: 14/07/2006 15:49:24 »
quote:
Originally posted by neilep

Fellow Peeps Of Adroit Goodness & Gifted Skill.

Say, I had a long piece of metal, say cylindrical in shape with a circumference of 8 inches...maybe made out of stainless steel.

Now, if i was to hit one end..how fast does the sound/vibration travel along the path ?



Sound travels much faster through solids (e.g. steel) than in gases( e.g. air):-



 

Offline neilep

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Re: Sound through a metal bar !
« Reply #2 on: 14/07/2006 15:51:48 »
Woooo !!..that's fast !!...thank you Robert !!.....

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ROBERT

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Re: Sound through a metal bar !
« Reply #3 on: 14/07/2006 16:17:03 »
quote:
Originally posted by neilep

Say, I had a long piece of metal, say cylindrical in shape with a circumference of 8 inches...maybe made out of stainless steel.

Say, for instance it was a mile long !!..would someone at the other end still hear it [?]



If you put you ear on a railway track, (not recommended), you will hear the train coming via the steel rail long before you hear it via the air. Perhaps when the train was a mile away.
« Last Edit: 14/07/2006 16:23:02 by ROBERT »
 

another_someone

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Re: Sound through a metal bar !
« Reply #4 on: 14/07/2006 17:45:15 »
quote:
Originally posted by ROBERT
If you put you ear on a railway track, (not recommended), you will hear the train coming via the steel rail long before you hear it via the air. Perhaps when the train was a mile away.



It also depends on the frequency of the sound generally, infrasound will travel far further, with less attenuation, than ultrasound hence you can hear the thump of a sub-woofer at distances where you cannot hear anything from the tweeter.




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Offline neilep

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Re: Sound through a metal bar !
« Reply #5 on: 14/07/2006 19:47:32 »
THANK YOU ROBERT & THANK YOU GEORGE.

So, from what you say there is indeed a limitation to the distance sound will travel through a solid metal rod, or perhaps our capability to detect it is the limiting factor here....still..what ever the case it..it definitely diminishes with distance....



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another_someone

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Re: Sound through a metal bar !
« Reply #6 on: 14/07/2006 20:50:54 »
quote:
Originally posted by neilep
So, from what you say there is indeed a limitation to the distance sound will travel through a solid metal rod, or perhaps our capability to detect it is the limiting factor here....still..what ever the case it..it definitely diminishes with distance....



Sound is like electricity, or most other things, it will travel through a conductor, but how far it will travel will depend upon the quality of the conductor, including its purity.

Metal is a better conductor of sound (depending on the stiffness of the metal) than air, but imperfection in the structure of the metal will dissipate the sound energy.  Beyond that, sound in air is usually omnidirectional, so will be subject to an inverse square law, or something similar (depending upon the exact pattern of dispersion).  Sound in an infinitely sized metal block would also be omnidirectional, but sound travelling through a rod whose cross section is smaller than the wavelength of the sound will be directional should have no loss of amplitude due to the spreading out of the sound, so the only loss would be due to imperfections in the metal itself.

That at least would be my understanding of the matter.



George
 

Offline neilep

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Re: Sound through a metal bar !
« Reply #7 on: 14/07/2006 21:43:07 »
THANKS GEORGE,

So, By your understanding...If a perfect rod was capable of being constructed to make a perfect conductorwould it provide a loss-less medium for sound to travel through over vast distances ?

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Offline Roy P

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Re: Sound through a metal bar !
« Reply #8 on: 15/07/2006 11:01:48 »
Speaking of sound: I just love loud music. However, I live in a terraced house (and always have done), which is not conducive to loud music.

Of course, I can use good headphones, which I do occasionally, but they're only second best, and you don't get that oooomph from the bass through your body. I was wondering if there's anything commercially available that could be used with headphones which simulates the 'physical' bass notes? Something that maybe straps around your waist?

There must be millions like me who love but can't play loud music because of their situation, so, for a budding entrepreneur, a product which simulates the bass could be a good money spinner! What would we call it?

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Offline neilep

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Re: Sound through a metal bar !
« Reply #9 on: 15/07/2006 12:51:15 »
Roy, There IS a product out there which does exactly what you want it to do.

For the life of me I can not remember where I saw it and it was quite a while back too...maybe a year or two...perhaps it was one of those gadget web sites like http://www.boysstuff.co.uk/  or http://www.firebox.co.uk/ or something similar.  Thinking about it..sorry I can not be of more help.

Of course, you could buy yourself a little sub-woofer and have it right next to your couch or the chair you sit on when listening to music, easy to hook up but would probably be felt next door too but not so loud as the high frequencies will be heard through your headphones.

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Offline Roy P

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Re: Sound through a metal bar !
« Reply #10 on: 15/07/2006 14:24:32 »
quote:
Originally posted by neilep
There IS a product out there which does exactly what you want it to do.

Maybe you're thinking of the vibrating chair, Neil? For one thing I can't sit due to a back problem so I was hoping for a more portable device. You are right though -- I forgot that.

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another_someone

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Re: Sound through a metal bar !
« Reply #11 on: 17/07/2006 03:12:12 »
quote:
Originally posted by neilep
So, By your understanding...If a perfect rod was capable of being constructed to make a perfect conductorwould it provide a loss-less medium for sound to travel through over vast distances ?



By definition, energy (including sound energy) has to go somewhere.  If it has nowhere to go, because the medium is lossless, then it will remain as sound energy in perpetuity.

Ofcourse, in the real world, nothing is ever totally lossless (maybe some sort of superconductor I don't know how that might behave to sound, but then it may well be that substantial sound energy might undermine its superconducting capabilities anyway).



George
 

Offline Atomic-S

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Re: Sound through a metal bar !
« Reply #12 on: 01/08/2006 05:30:50 »
Light can now be sent through a fiber optic cable which is of considerable length, due to its extremely low loss. That would have once been considered highly unlikely. What is the limit on sonic conductivity of solids? I don't think anyone knows.

By the way, speaking of bass units: I think I may have heard of such a unit by the term "Buttkicker"; am not sure. In any case, such a unit might be attached to one's bed or couch, rather than chair. Be careful however because depending upon the construction of your building, the noise might propagate into adjacent units through  the structure.
 

Offline Atomic-S

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Re: Sound through a metal bar !
« Reply #13 on: 14/08/2006 04:46:38 »
quote:
It also depends on the frequency of the sound generally, infrasound will travel far further, with less attenuation, than ultrasound hence you can hear the thump of a sub-woofer at distances where you cannot hear anything from the tweeter
Well, that may be true of a straight rail floating in space, but for one fastened to the ties, the fastenings will materially affect its properties, and my suspicion is that its usefulness as a conductor of low frequencies will rapidly diminish below some frequency.
 

Offline eric l

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Re: Sound through a metal bar !
« Reply #14 on: 14/08/2006 10:04:04 »
Apparently, many people draw too close a parallel between sound waves - which are material deformation - and electromagnetich waves - such as light or radio waves.
When you apply a force to on abjoect, this results in deformation.  Now either the object is a solid, or it is a liquid.  If it is a solid, the deformation is proportinal to the intensity of the force (Hooke's law), if it is a liquid the rate of deformation (in time) is proportional to the intensity of the force, and the deformation is further proportional to the duration during which the force is applied (Newton's law).  These are the basic laws in rheology (the science of flow or deformation)
Lots of objects are actually visco-elastic :  they are neither perfect liquids ("visco") nor perfect solids ("elastic") but something in between, like gels, puties...  It will depend on the intensity of the force wether they will behave more like elastic or more like viscous.
With sound, we apply a force that is not constant, but alternating (like alternating current).  In a perfect solid, the deformation will be completely in phase with the force, in a perfect liquid the deformation will be completely out of phase. In a visco-elastic medium, we have to add up this two, and because they are out of phase, we have damping.
Padding is done by alternating rheologicaly solid materials with rheologicaly liquid materials (air mostly) which causes the damping.
Within the range of forces applied here for sound propagation, a metal rail is a perfect solid.  It will be less perfect when you have to fix it ties or sleepers, which in turn lie on a bed of stones as in the case of a railway.
 

another_someone

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Re: Sound through a metal bar !
« Reply #15 on: 14/08/2006 11:38:48 »
quote:
Originally posted by Atomic-S
Well, that may be true of a straight rail floating in space, but for one fastened to the ties, the fastenings will materially affect its properties, and my suspicion is that its usefulness as a conductor of low frequencies will rapidly diminish below some frequency.



If one is looking at the acoustic effects of the ties, one would also have to look at the acoustic effects of what it is tied to, and the whole thing becomes a far more complex system.

In any case, one would have significant effects as the wavelength of the sound approached the length of the metal bar, and if it had intermediate ties, then one could set up resonances between the ties, and thus begin to have effects as the wavelength of the sound approached the distance between the ties.



George
 

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Re: Sound through a metal bar !
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