??
You are comparing water in a bathtub (that you somehow manage to set in motion in one direction only) to a sound source within a pipe.
What if the source is 1/3 of the way down the pipe?
Now we have smoke, where are the mirrors?
Anyway, this is getting ridiculous. If what I'm saying isn't obvious by now, it never will be - I can't explain it any simpler.
My analogy was a mirror lined pipe😀 So yes it had it all😉
In all seriousness, the smoke for me was easier to visualize than stuff with lots of mass etc..
In all seriousness, the smoke for me was easier to visualize than stuff with lots of mass etc..
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Excuse me! Where have you been? We've understood that for almost 100 years now. Einstein? Heard the name?
Why not accept the obvious? It reflects. It's so simple. Why go to lengths trying to explain it another way?
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I perhaps used the wrong word, instead of "clear" I should have used "definitive".
"Theory":
1 : the analysis of a set of facts in their relation to one another
2 : abstract thought : speculation
3 : the general or abstract principles of a body of fact, a science, or an art <music theory>
4 a : a belief, policy, or procedure proposed or followed as the basis of action <her method is based on the theory that all children want to learn> b : an ideal or hypothetical set of facts, principles, or circumstances
I have a theory that I've been discussing for the past few pages - is it definitive?
Anyhow, I've gotta go do stuff, a beautiful day here and I have tons to do. I leave you gentlemen of distinction to invent more ways to explain the obvious. 😀
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I'll agree with John that sound waves bounce off the walls of the pipe.
While a large piston can send plane waves down a pipe, a small speaker at the end of a wide pipe will radiate sound in all directions and this will bounce off the walls.
However, at low frequencies, where the wavelength is much bigger than the width of the pipe, the reflections combine in such a way that no interference patterns are visible, and it looks like a simple wave traveling straight down the pipe.
To see the effect, try playing with that wave applet again. Draw a pipe in front of the wave source and adjust the "frequency" control to get different wavelengths.
btw, Using the "crayon" tool in that applet, I struggle to make straight lines, let alone horn flares. Is there a way to draw neatly?
While a large piston can send plane waves down a pipe, a small speaker at the end of a wide pipe will radiate sound in all directions and this will bounce off the walls.
However, at low frequencies, where the wavelength is much bigger than the width of the pipe, the reflections combine in such a way that no interference patterns are visible, and it looks like a simple wave traveling straight down the pipe.
To see the effect, try playing with that wave applet again. Draw a pipe in front of the wave source and adjust the "frequency" control to get different wavelengths.
btw, Using the "crayon" tool in that applet, I struggle to make straight lines, let alone horn flares. Is there a way to draw neatly?
Attachments
Our theory of gravity is "definitive". It has held up to every experiment to the resolution of our instrumentation. Because you don't understand it does not mean that it is not understood. This is a classic failing in all your arguments.
John,
There's a spectrum involved. The medium has different energy transmission abilities, dependent upon the frequency.
At 20 Hz, think foamy whipped cream. In a tube. Not at home where you can do as you wish. 😉 Press(ure) on one end (and it) comes out the other.
At 20 kHz, the medium's response to the acoustic energy is different. Things are reflected to a higher degree. They bounce back. Martin generalized as ~500 Hz....maybe more, maybe less...So the amount of reflection increases with frequency, just not all at once, at one point.
The same laws are present wrt baffle diffraction step. The amount of effect varies wrt frequency. The amount of compensation we dial in offsets this.
The TL is used for its benefits below 500 Hz.
The resonances above those wanted are designed out or damped.
Are we still having fun? Does Mongo need to make an appearance?
There's a spectrum involved. The medium has different energy transmission abilities, dependent upon the frequency.
At 20 Hz, think foamy whipped cream. In a tube. Not at home where you can do as you wish. 😉 Press(ure) on one end (and it) comes out the other.
At 20 kHz, the medium's response to the acoustic energy is different. Things are reflected to a higher degree. They bounce back. Martin generalized as ~500 Hz....maybe more, maybe less...So the amount of reflection increases with frequency, just not all at once, at one point.
The same laws are present wrt baffle diffraction step. The amount of effect varies wrt frequency. The amount of compensation we dial in offsets this.
The TL is used for its benefits below 500 Hz.
The resonances above those wanted are designed out or damped.
Are we still having fun? Does Mongo need to make an appearance?
I'll not argue that point with you - it's not what this is all about. If you wish to dwell on it for deflection purposes (you don't have any "definitive" answers for my questions, despite this being your field of expertise) that's up to you.
I've seen it all before - next there will be some nit-picking about my spelling or grammar - anything to latch onto to discredit. Typical.
Ed,
The specific mechanism that has the wave moving down the pipe and going around the bend is what I'm interested in - leave all of the other detail out and just focus on that. We are still talking about sound waves, right? Do they make a magical transformation at a lower frequency into something more substantial, more viscous, more mystical? I don't think so.
As for having fun, I'm keeping my cards close to my vest...😀
Well, we thought that about Newton's theory for a while, too, even called it a law.
But that's beside the point: The model works. This is a particularly good example, because there's a simple model that mostly works, and a more complex model that covers a few edge cases.
Absolutely
The sound waves change only in frequency. The medium's ability to transmit them changes, wrt frequency.
Letting go, stopping the control freak tendencies is one of the things that torments me...
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Set a single frequency - 20hz for example (we like keeping it simple). Does air as a medium support a 20hz sound wave? No question, right?
The issue is whether this 20hz sound wave will reflect from a solid surface at close proximity. That is the point. Leave whipped cream or smoke behind and talk about sound and its ability to reflect from solid objects.
Yes. Apparently his theoretical predictions agree quite well with experimental results. Actually even better than previous theories that were also considered "correct" in their time.
The trouble is that "definitive understandings" tend to change over time.
Around the end of the 19'th century, the scientific community thought they had their understanding of physics pretty well nailed down, with just a couple of loose ends to tidy up. Then it all unraveled...
I think there's more "loose ends" now than there were then.
hehehe
The applet is done under the assumption that the tube is frictionless. In reality, it is not frictionless, and can vary quite significantly.
Take a woofer and place it 10 inches from a concrete wall. Play a 20hz tone through the woofer - what happens next? Does the sound wave fully go through the wall? Does it reflect? My limited experience says it will reflect.
So, if it will reflect from a solid object out in free air at close proximity, why not within a pipe?
I think whipped cream was suggested as an alternative.
You're missing a lot, John, if you haven't yet enjoyed a "mystical experience" involving whipped cream.
I think we're getting a little off topic here, though...
😀
John, let's establish what some of my "generalizations" include.
Reflect as from a mirror, a one to one transmission of the original. That's the absolute..in acoustics we must bend things a little.
some of it turns into heat in the wall,
some of it is pushed axially along the wall, it changes direction by 90 degrees and is distributed into the surroundings,
some of it, due to the pressure gradient, starts being reflected away from the wall, it changes direction by more than 90 degrees,
some of it can be considered to reflect, changing direction by 180 degrees, this is minor, considering the gross area available for dispersion of all the energy...is it significant?...maybe absolutely...probably not on balance
Reflect as from a mirror, a one to one transmission of the original. That's the absolute..in acoustics we must bend things a little.
The energy becomes distributed:
some of it turns into heat in the wall,
some of it is pushed axially along the wall, it changes direction by 90 degrees and is distributed into the surroundings,
some of it, due to the pressure gradient, starts being reflected away from the wall, it changes direction by more than 90 degrees,
some of it can be considered to reflect, changing direction by 180 degrees, this is minor, considering the gross area available for dispersion of all the energy...is it significant?...maybe absolutely...probably not on balance
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