The pipe is rigid and relatively thick and unstrechable. Sure, the pressure impulse pushes against it but not much energy is transferred becuz the pipe wall isn't stretched significantly: No movement, no energy transfer.
But your eardrum is very thin and stretchable and will move with very small, exceedingly tiny, pressure changes.
I fail to see what your difficulty is.
Perhaps you are overthinking this.
You don't seem to have difficulty applying the same principle to your latest speaker where you have designed extremely rigid sidewalls.
I thought that MJL just liked to play devil's advocate and stir up merde. But, having read his wave bouncing arguments, I think that might be just what he's picturing.
Seems to me it depends on pressure and volume, and that every each frequency has an ideal volume
The wider FR band, the more its compromised
btw, we dont hear exstremely low frequency, right
But our body reacts on it
Its been proven that we get sick or uncomfortable, anxiety etc
Cause can be traffic and buildings, bridges, tunnels, etc
Whales use such exstreme low frequencies to communicate from one end of an ocean to the other end
Its a fact that wind and water acts alike, especially with regards to turbulence
A special dinosaour is claimed to have had the same ability as whales, to communicate over exstreme distances using exstremely low frequencies, only that was on ground, in air
But really, whether its a soundwave in air or water, cant be the same as actually moving air or water, like wind and waves
So, how is it possible fore exstreme low frequnency signals to travel over huge distances ?
The wider FR band, the more its compromised
btw, we dont hear exstremely low frequency, right
But our body reacts on it
Its been proven that we get sick or uncomfortable, anxiety etc
Cause can be traffic and buildings, bridges, tunnels, etc
Whales use such exstreme low frequencies to communicate from one end of an ocean to the other end
Its a fact that wind and water acts alike, especially with regards to turbulence
A special dinosaour is claimed to have had the same ability as whales, to communicate over exstreme distances using exstremely low frequencies, only that was on ground, in air
But really, whether its a soundwave in air or water, cant be the same as actually moving air or water, like wind and waves
So, how is it possible fore exstreme low frequnency signals to travel over huge distances ?
Your conceptual problem is, I think, with the word "wave." In a dimension small with respect to wavelength, there is no "wave," the medium is nearly isobaric (other than at a thin boundary layer).
Let's do a reductio ad absurdum, then walk back from there. Imagine your folded box. Seal off the far end. Now, on the "driving" end (the argument works perfectly well when the box is driven else where), start releasing pressurized gas over the course of a second or two to bring things up to 2 atmospheres. What happens to the pressure at the far end?
I think that the problem is that MJL21193 is right and he's not right. What he is saying is correct when taken as a precise statement, but it's a gross over simplification of the situation. It's like saying "the world is round because flat is hard to do". Yea, and ?
In my previous post its clear that I find low infra sonic waves interesting
They travel/propagate long distances
Again, its a fact they can be created by buildings and tunnels etc
And it stays there, thus its also clear that ultrasonic waves can be a standing wave, caused by a tube
Tho, I think I read somewhere that standing waves has nothing to do with reflection, but merely a cause of a defined space/volume
But the space where infra sonic sound caused by buildings occur is not a confined one
One particular place where it occurs are tunnels, and they are open at both ends
What makes it different ?
What happens if we place a woofer in the middle of an open ended tube ? 😕
Will it "ressonate" exactly as if the woofer was placed at one end, or even better ?
btw
I remember once I had an empty woofer box, with no woofers, placed in my room
I could actually hear a difference when I placed a pillow in the empty box
And I remeber another incident from a party
A couple of Lowther horns with Fostex fullrange driver were placed in the room
It was a very big room
They were not connected to anything, just standing there
Yet, suddenly the owner shouted, "my Fostex drivers are moving, and a hell lot"
We placed a pillow in the horn mouth, and problem solved, drivers stopped moving
They travel/propagate long distances
Again, its a fact they can be created by buildings and tunnels etc
And it stays there, thus its also clear that ultrasonic waves can be a standing wave, caused by a tube
Tho, I think I read somewhere that standing waves has nothing to do with reflection, but merely a cause of a defined space/volume
But the space where infra sonic sound caused by buildings occur is not a confined one
One particular place where it occurs are tunnels, and they are open at both ends
What makes it different ?
What happens if we place a woofer in the middle of an open ended tube ? 😕
Will it "ressonate" exactly as if the woofer was placed at one end, or even better ?
btw
I remember once I had an empty woofer box, with no woofers, placed in my room
I could actually hear a difference when I placed a pillow in the empty box
And I remeber another incident from a party
A couple of Lowther horns with Fostex fullrange driver were placed in the room
It was a very big room
They were not connected to anything, just standing there
Yet, suddenly the owner shouted, "my Fostex drivers are moving, and a hell lot"
We placed a pillow in the horn mouth, and problem solved, drivers stopped moving
tinitus, a standing wave requires boundary conditions with dimensions comparable to wavelength. In a simple-minded sense, if we consider to rigid, parallel boundaries spaced apart by a distance a, the velocity at the boundary is constrained to be zero, right? So given that, the lowest frequency that can form a standing wave is one where particle velocity is zero at two points spaced by a, which would have a wavelength of 2a.
Now, if we have perpendicular boundaries spaced by b, we can then have a standing wave perpendicular to the original one, but with the longest wavelength of 2b. So in a real sense, it is indeed a property of the "space," or more precisely, the boundary conditions.
Now, if we have perpendicular boundaries spaced by b, we can then have a standing wave perpendicular to the original one, but with the longest wavelength of 2b. So in a real sense, it is indeed a property of the "space," or more precisely, the boundary conditions.
The ripple applet can generate plane waves (line source).
Incidentally, I've done some reverse engineering on the format of the applet's import/export format. If anyone's interested, I can start a new thread with it.
Yes, and boundary conditions are the same fore a tube, be it closed or open ended
It doesnt matter whether its closed or open ended
Other than the fact that an open ended tube can be exited from outside, which the closed ended one cannot
And that there will be the same standing wave in a tube, be it open ended or not, it doesnt matter
btw, thats the nature of a good matrix box design
Space devided into lots of smaller volumes, thus no standing waves
Can there be high frequency standing waves
No ? only reflections, right ?
Is there a grey zone ?
And where ?
Can a standing wave go around corners ?
No ?
Or does it just excite the neighbour space ?
Hmm, my mentor once said that a speaker with a passive slave is designed correct when the slave is moving the same way as the driver
I always wondered how that would be possible
A pulsing standing wave
I always wondered how that would be possible
A pulsing standing wave
Well my problem is that I think at all, apparently, rather than accept the stock explanation. Believe me, I understand "the right way", I just don't agree with it. There are inconsistencies that haven't been accurately explained thus far.
It is said that I am oversimplifying it but the reverse is true - I've attempted to simplify it by limiting it to a single frequency from one source but in reality it is much more complex than that. From the instant the driver starts to emit sound there is a chain reaction - energy is transfered to the air which makes it vibrate which in turn (with some impedance mismatch losses) makes the pipe vibrate as the energy is transfered to it. The pipe movement emits its own "sound" and its decay time is longer (depending upon how well damped it is). There are reflections because waves at any frequency tend to propagate straight out from the source until an obstacle or barrier causes it to change direction via reflection and refraction.
You all would have it that the energy enters the pipe and as coherent as a laser beam between parallel mirrors only bounces back and forth from end to end without having any effect on the pipe itself. Nonsense.
That a ridiculous analogy Sy. Truly. There can be pressure without "sound" you know. There is no "sound" without energy transfer.
Depends. At resonance, the driver should barely move and the slave/passive should be moving at its maximum. Below resonance, the slave/passive goes opposite to driver motion. And above resonance, the slave/passive should barely move and the driver should be doing all the work.
Sounds like it would be a no limit Xmax design, if realistic
But I dont understand how you can say the passive moves, when the driver doesnt
Oh, other than a passive really is excited by standing wave, and not by driver ?
Well, I suppose that was my guess when bringing it up, and you say it is
And due to the low Fs of the passive, it produces lower frequency than the standing wave that excited it
But I dont understand how you can say the passive moves, when the driver doesnt
Oh, other than a passive really is excited by standing wave, and not by driver ?
Well, I suppose that was my guess when bringing it up, and you say it is
And due to the low Fs of the passive, it produces lower frequency than the standing wave that excited it
Being right, even if I'm not right is a step in the right direction...😉
I see it all the time here - the inside of a speaker is treated like a duct to accommodate the passage of air. When I point out that it's not air flow that you need to be concerned with, fellows get flustered and upset - all of that time spent to radius the corners of the holes through the braces was wasted? Yer nuts buddy...
Sound passing through the air is not like wind from a fan, it's not like water flowing through a pipe.
Oh and the Earth is round because of gravity, not "just because".
😀
Note that I used the word "barely." That's what resonance is all about, the driving force for maximum effect is at a minimum, if that makes sense to you.
It's not a standing wave that excites it (note that VOLUME is the critical parameter in these calculations, not pathlength!), the air mass plus PR move as a fairly unitary mass.
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