Why Does Sound Propagate?

notauser said:

Keep the Leyden Jars away from the Van deGraff, and you're pretty safe.. I'd love to see the VandeGraff generator that defies that rule though..

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My brain was warped before. Now and after reading about it I am blitzed. Listening to people and learning concepts have been fundamental with me for a long time. Conception is one thing. But, Modeling for the purpose of Scientific Development is another. But to even participate at the outer circle is an inspiring and exiting experience.

Thank you.


kv

Mining with venturi vortex mechines.

United States Patent: 7040557

This machine is used for extracting moisture. But.

I have a friend who told me he created one of these it was a 4" inch assembly and he was able to fine tune it. Instead of hurling media with two opposing exit tubes typically for smashing rocks together and extracting the silver and gold from left over mining product.

He said Quote: I was able to accelerate wheat down the tube and when it exited and hit the atmosphere it would shed the outer shell and pulverize into flour.


I really didn't want to believe him. But, stranger things have happened.


kv

Delusion and Delirium

notauser said:

You aren't in denial, but so many are..

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Who said I'm not in denial? It's a filthy lie.

I like to think of myself as an "amateur" jack-of-all-trades-master-of-none. Amateur becase I have limitations of skill, interest, inherent ability and perseverence. Through it all I've struck an equilibrium that works pretty well for me.

I don't hunger for the ultimate knowledge of a subject. At the same time, if I have an interest in it (or, if it is something I seem to need to know to understand something else) I'll pursue it...at least to the next level. That's what I'm trying to do here with the sound propagation thing. I didn't just, out of the clear blue sky one day, say, "I think I'll learn more about sound propagation" and hit the internet. I was thinking about directional microphones, for a project, and how allowing sound energy to come back to the back side of the diaphragm is able to give directionality. For a single frequency or a narrow band of frequencies, it's pretty easy to see the magician's assistant hiding behind the smoke and mirrors but, to do it across the audio spectrum seems a lot harder. Pretty mundane, huh?

They say that some folks thirst after the ultimate truth and some thirst after ultimate power. I tend to thirst after the same thing all people thirst after...salted nuts.

So, anyway, I don't want to lead you on thinking I'm on some noble quest. But, I do appreciate your input and feel like I am learning more about the subject and, while I'll never be an "expert", would like to at least bolster the illusion that I know a little bit about it. And, to that end...to forge ahead...although I can see that this thread is definitely "drifting" and I'm not sure how long it can hold onto its original thrust...

Sorry, I was just leaving...

killivolt said:

But to even participate at the outer circle is an inspiring and exiting experience.

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Uhm...not wishing to presume to put words in your mouth but, are you sure you had intended to use the word, "exiting" in this instance?

The other side of the academic tracks

notauser said:

Yea, but Stephen Hawking has done more to destroy physics these days than anything else.. His laymans explanations of everything often side-track actual students waay too much.

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But, I guess the other side to the, "Hawking Saga" is that a lot of people who just wouldn't have any real means or aptitude to access this kind of stuff through conventional acadamia, have at least a watered-down version of it and, surely some people who may have gone into other fields have been inspired to continue on to more lofty planes. Plus, (okay, I consider it a plus), it gives people like me a way to at least feel more educated.

Actually, I think the computer (and, computerized manufacturing methods) have done more damage to the engineering community than just about anything else. It's not easy to design and build something when a better one can be bought for a couple of (insert your basic unit of currency)s. Especially, when just one component may very well cost more than that.

I found this place on the internet called, Deal Extreme that sells cheap stuff cheap with free shipping. Anyway, I got a 4 input, PCI video surveilance board. It's like less than $14...delivered from Hong Knong. But, it has BNC inputs. But, DX sells BNC to RCA adapters (in quantity of 10) for $0.58 each. How do you do anything except buy it?

All of which, of course, has nothing to do with sound propagation so, I'll stop this sidebar.

Bums me out too that corporate mass production takes alot of practical purpose from alot of projects..
I'm separating ppl like you from ppl who have paid a few thousand dollars in tuition to be assigned grueling amounts of math/physics in order to become employable in the field.. You're right, some ppl just aren't cut out for it, and will inevitably flunk out, but others are just too busy dwelling on M-Theory analogies when they should be studying differential equations.. Alot of these guys are smart enough to slide along for a while with virtually no actual work, but that wall approaches quickly and without warning..
The only thing I don't like about generally interested ppl reading Hawking, is I so often end up in remedial debates, having to explain the problems I see with their new theory of why the big bang occurred etc..

One of my favorite quotes ever was made by my optics professor.. On the first day of class he was ranting about the same thing I am now.. He said:
"There are perhaps three paychecks for abstract theoretical physics in the world today, and Stephen Hawking collects two of them.."

crashsite said:

Uhm...not wishing to presume to put words in your mouth but, are you sure you had intended to use the word, "exiting" in this instance?

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That's strange I'm feeling a little punny` at the moment.




Tell me ...... ? you were just teased to deviation.

The Perverse Nature of Matter

killivolt said:

Tell me ...... ? you were just teased to deviation.

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No...but, I have heard it commented that I'm a bit of a deviant...

Some day's are like that ........

The Perverse Nature of Matter

crashsite said:

No...but, I have heard it commented that I'm a bit of a deviant...

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Like when your on a project and the part's design spec's say (this) and ends up (that).


kv.........Carry on whooa !

Quotable Quotes

notauser said:

The only thing I don't like about generally interested ppl reading Hawking, is I so often end up in remedial debates, having to explain the problems I see with their new theory of why the big bang occurred etc..

One of my favorite quotes ever was....

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Okay. Note to self: Don't bring up your, Trillion Year Old Universe theory.

Oops.

Perhaps not one of my favorites but, a memorable quote by one of my teachers: "What's the matter...do you need glasses?". Interestingly, not an optics professor...

So, anyway. In summary, we have at least three rates or speeds identified. The thermal movements of the air molecules (sticking with air), at random rates, within a range, and in the GHz range), the movement of (usually) a subsonic disturbing force in the air mass (such as a speaker cone, vocal cords, a tree falling in the forest, etc.) and a sonic wavefront that propagates away from the disturbance at a fairly specific speed (around 1100 fps). So far these speeds seem to be pretty much unrelated to each other although I suspect that there is some corrolation between the GHz stuff and the sonic speed stuff. At this simplistic level, are these observations true?

Yea I think you got that pretty close in context actually.. Does your conceptual picture have the distance the particles travel in their high frequency oscilations much shorter than low frequency oscillations?

Moving Air

notauser said:

Does your conceptual picture have the distance the particles travel in their high frequency oscilations much shorter than low frequency oscillations?

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Well, yeah. The thermal vibrations are constrained to within the dimensions of the distance between the air molecules. The motion of the disturbing force would be millions or even billions of times larger displacement as fairly massive amounts of air molecules are moved great distances.

I suppose we've all blown at a spider web some several feet away and noticed that it takes some time for the burst of air to reach it and it makes sense that the air extending in front of a speaker moves in a gross sort of way as well.

Here's where I start having problems with the terminology and it may just be a case of semantics. The very use of the word, "wave" conjuures up visions of repeating, cyclical events (you use the term, "oscillations" above). The notion of, "longitudinal waves" and the compressions and rarefactions re-enforce that picture.

But, it seems that to understand the sonic wavefront (for lack of a better term), one must think of the movement of the disturbing force on an instant-by-instant basis with the sonic waveform also being developed on an instant-by-instant basis.

I'm 100% positive that a copy of the disturbing force is formed in the air and travels (propagates), at the speed of sound, intact. Of course, as it travels, it's acted upon by many factors that attenuate and smear it.

Even so, when it hits a reflective surface, it continues to retain the time vs. pressure characteristics of the original disturbing force. I know this is true because I can hear that it's true when I hear an echo. The, "hello" I yell at a rock face comes back as, "hello".

Because the sonic wavefront is a copy of the original, it must also at least start with a similar displacement of air molecules and, presumably, as it attenuates over time, will have a smaller and smaller amount of displacement until it dissipates to the dimensions of the thermal movement.

Hopefully, there's validity to at least some of that.

crashsite said:

Well, yeah. The thermal vibrations are constrained to within the dimensions of the distance between the air molecules. The motion of the disturbing force would be millions or even billions of times larger displacement as fairly massive amounts of air molecules are moved great distances.

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Great compared to the distance between molecules but small comparted to the distance traveled by the sound energy.

The air in front of a speaker is displaced by at most 1 wave lenght. I do not know why you mentioned blowing and the related speed.

Other then that it sounds about right.

In the context of the model, drifting air in the mass would have to be thought of as 'extremely' low frequency oscillation.. Remember what I was saying about like interfering mainly with like frequencie wise.. Drifting air will alter the action of other drifting air quite a bit, but as far as the higher frequency action is concerned, drifting air is pretty much the same as dead air.. It will interfere with sound a bit more than even higher frequency action though.. It can be analogized like radio/tv stations, or anything that uses channels.. Channels are separated to avoid too much interference, but if you've ever used a tv without cable you may have seen times of bad reception where one channel's image seems to be ghosted overtop of another channel.. Its because their bandwidths are overlapping, the desired channel isn't tuned in discreetly enough.. I've seen it on cable a few times to, but not digital..

crashsite said:

So, by that logic the piece of music that the orchestra plans to play tonight at Carneie Hall already exists? It's just necessary for the musicians to place their instruments into the air mass and the music will "repressurize" and become audible to the audience? Or will the musicians still have to painstakingly form each note and vibrato with the instruments?

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I see it differently. It's those audible frequencies that I believe exist at all times and not their relationship to each other. The musicians just create the anomaly by which we can hear them. (I am also a musician and it's not so painstaking because it is so pleasing a thing to do.)

Another example is this: The spectrum for any frequency exists at all times. e.g., ~630 Nm. Our friend, Nick Holonyak Jr., just invented the anomaly (the red LED) which provides us with another proof that it exists in Nature.

Thanks Crash, for your respectable response. If you need anything , just holler. --

In a way you're right, but at ambient intensities, the vast majority get interfered into obliteration.. Resonant frequencies however will stand out.. Any space will have natural frequencies dependant on the placement of walls etc.. Audio engineers design rooms accoustically based on principles like these.. Harmonics, and harmony now come into play.. Thats why ppl pay so much to rent recording studios when modern software can mimick the equipment..
These things are explained by resonance and standing waves, and to some extent Fourier analysis.. Now Fourier transforms can be some of the toughest math out there, but alot of sites explain it pretty well in near laymans terms.. If you learn a bit about resonance/standing waves (or already know that stuff) then you should be able to get the conceptual gist of Fourier transfoerms.. His work is the backbone of signal processing, but also goes waaay beyond that..

Yellow brick road.

The further we go the more interesting it gets.


I'm wondering when will get to the Wizard or Maybe Dorothy will finally wake up ?

Crashy. I think my water is finally holding itself without the bucket.


kv

I'm about at the extent of my comfort level.. I haven't done much nitty gritty work with waves in a long time..
I gotta stress again though the convenience of learning the math principles behind this.. When you got that down it gets really easy to learn all kinds of concepts because its hilarious how many physical systems obey a few basic models.. Actually, a major concept in modern/quantum physics is that waves can be used to describe EVERYTHING!! (Read up on deBroglie if interested in that)..
And on a more practical level, all those things I used to analogize, like springs, microwaves, TV/radio, cars in driveways, engine vibration and on, and on and on, can be properly modeled and explained with the same basics.. Wave mechanics are like the arithmetic of the universe..

notauser said:

I'm about at the extent of my comfort level.. I haven't done much nitty gritty work with waves in a long time..
I gotta stress again though the convenience of learning the math principles behind this.. When you got that down it gets really easy to learn all kinds of concepts because its hilarious how many physical systems obey a few basic models.. Actually, a major concept in modern/quantum physics is that waves can be used to describe EVERYTHING!! (Read up on deBroglie if interested in that)..
And on a more practical level, all those things I used to analogize, like springs, microwaves, TV/radio, cars in driveways, engine vibration and on, and on and on, can be properly modeled and explained with the same basics.. Wave mechanics are like the arithmetic of the universe..

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Interestingly accurate analogy.

kv

I liked that when I typed it too.. I was thinking about Einstein's quote "If mathematics are the language of the universe, then algabra is the language of God.."