This is the post that started all this.
Look at what I'm saying: the pipe resonance (not the pipe at all but the contained column of air within the pipe) needs energy. Up to this post, the idea being thrown about was that the wave (being of long wavelength) would bounce back and forth from one end to the other, whether they were open or closed. This is fine but too much energy is lost - not enough will remain within the pipe to excite the column of air to resonance.
Looking at the java applet posted earlier demonstrates my point very nicely. Add walls to the ap and witness how agitated the medium is with all of the reflection that is taking place. Here there is enough energy to excite the air to resonance.
What's important about the pipe is its length.
The volume of air. The mass of the air. The mass determines the resonance point. The presence of the pipe walls serves to define the limits of the medium under the influence of the sound wave. The effect of the pipe walls may be real, but in relation to the effect of mass of the medium...the walls can be considered insignificant...having no bearing upon what we want to accomplish in a resonant column.
We still at 20 Hz? The applet doesn't apply
Edited for clarity
The volume of air. The mass of the air. The mass determines the resonance point. The presence of the pipe walls serves to define the limits of the medium under the influence of the sound wave. The effect of the pipe walls may be real, but in relation to the effect of mass of the medium...the walls can be considered insignificant...having no bearing upon what we want to accomplish in a resonant column.
We still at 20 Hz? The applet doesn't apply
Edited for clarity
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If you throw a 4" nerf ball in a room, it will bounce around. If you stuff it down a 3.5" mailing tube, it's not going to bounce off the walls of the tube.
To say it "reflects off the walls" implies an angular component that I don't think there's room for, assuming a 56 foot wave in a (for argument's sake) 1 foot pipe.
It does if you send a plane wave down a long pipe. Even with horns, friction will make a difference. The amount of difference depends on roughness versus wavelength.😎Sure, trying to figure things out can drive people mad.😀
??
What does friction have to do with it?
Is this a madhouse?
😀
I feel really special: I got a direct, private email from him threatening me with a lawsuit for invasion of privacy and stalking because I stated his given name and "mentioned" his email address. DIYAudio moderators removed his name from the post, which was fine with me, and I never listed his full email address, just the part that included his name.
Paul
Paul
>>Over the past few months, I've been approached -actually, harassed would be a more apt description, by some folks claiming to be Transmission Line "experts" after I offered some observations regarding apparent errors in published data by a well regarded industry expert - George Augspurger.
I really do wonder if there are no other more pressing problems on planet earth than the TL problem ... 😀
Lets face it- speaker building and the physics behind it is not exactly rocket science nor quantum physics. Everyone who thinks there is magic, special abilities and some kind of deeper truth and mystery involved should go to the madhouse.
Starting a fight over t- line theory ... yaddayaddayadda i dunno how long that soup has been cooking but its rather uneatable and of no greater concern really. A few decades ago i might have said sth else, but sometimes wisdom comes with age 😱 One could also assume that some peeps simply grow tired of the endless (and most importantly senseless) battles between t-line theory 1 and 2 and 3 and xxx1000.
Cheers
I really do wonder if there are no other more pressing problems on planet earth than the TL problem ... 😀
Lets face it- speaker building and the physics behind it is not exactly rocket science nor quantum physics. Everyone who thinks there is magic, special abilities and some kind of deeper truth and mystery involved should go to the madhouse.
Starting a fight over t- line theory ... yaddayaddayadda i dunno how long that soup has been cooking but its rather uneatable and of no greater concern really. A few decades ago i might have said sth else, but sometimes wisdom comes with age 😱 One could also assume that some peeps simply grow tired of the endless (and most importantly senseless) battles between t-line theory 1 and 2 and 3 and xxx1000.
Cheers
Yeah, I noticed your post getting modded and Cal's getting deleted. Sy seems to have gotten away with it here, though: 😀 http://www.diyaudio.com/forums/multi-way/161961-real-expert-just-self-proclaimed-25.html#post2107863
I respect the legal right to privacy and agree that his name wasn't relevant to the thread (although it's a heck of a lot easier to spell than his screen name).
What completely baffles me is why anybody would be so paranoid about their privacy as to not even want their first name mentioned in public. 😕
Sometimes I think there's as much to be learned about psychology as audio in these forums...
notice the low frequency wave front shape changes? reflection. this is also because a point source is being used.
I wonder how he'd manage that having willfully provided the information to a public domain? In any case he threatened me with the same thing when he was kind enough to call.
Yes I deleted and modded them while we were still on the phone as it sounded like there was foam coming out of his mouth and I thought it's not right to treat electronics like that.
Right so if there is a mass loading (ie: pressurizing or density increase) rather than a point source there's no reflection, correct?
I guess Villa doesn't know I don't have access to passwords and that this kind of info is easy to find if you just look.
General Asylum - RE: Most folks - cjgavin@gmail.com - March 06, 2010 at 06:42:45
General Asylum - RE: Most folks - cjgavin@gmail.com - March 06, 2010 at 06:42:45
None would be seen in the quarter wave length tube for sure under normal frequencies where the wave length is longer than the circumference of a round tube. Above such frequency, symptoms of a point source begin to appear.
You guys still talking? The nerf ball analogy solved the mystery and answers all of the questions.
😉
😉
I've already been out and bough a bunch of stuff, come back, built a fire and did some major cleaning in my shop...time diff Cal. Break time right now - all work and no play makes Johnny a dull(er) boy.
😀
😀
Pipe diameter tough question:
Is the resonant frequency of a 10 foot diameter pipe the same as a 10 inch diameter pipe of the same length?
How about a 1 inch diameter pipe in comparison to a 10 inch diameter pipe of the same length?
What is it about these pipes that makes them resonate at different frequencies if they are still the same length from end to end?
Gotta go check on my fire.
Is the resonant frequency of a 10 foot diameter pipe the same as a 10 inch diameter pipe of the same length?
How about a 1 inch diameter pipe in comparison to a 10 inch diameter pipe of the same length?
What is it about these pipes that makes them resonate at different frequencies if they are still the same length from end to end?
Gotta go check on my fire.
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