- Posted by David Aiken (A) on March 07, 2007 at 14:27:18
In Reply to: Re: I was hoping some technical explanation might appear.... posted by Ethan Winer on March 6, 2007 at 06:44:27:
Ethan,OK, I can accept those arguments—with a caveat I'll come to—and most especially the one about the number of Sabins absorption required. I think you were a little kind on this point, however. You failed to mention that the preservation of a similar response profile to the original room would require that absorption to have exactly the same absorptive spectrum as the original room. Given the huge variation in absorption 'spectrum' of all the rooms out there in the real world, the likelihood of a passive device being able to mimic all of them is going to be non-existent.
So to the caveat. What if absorption isn't the method used to achieve results with these products? The explanation I read referred to an application of the venturi effect. The venturi effect is based on pressure and relies on a sudden transition between high and low pressure zones caused by a mechanical restriction. What we're seeing in the plots is a reduction in sound pressure levels and that translates into a reduction in variation of air pressure within the room. Venturis don't use absorption to achieve their pressure change .
I can't see how these things could introduce a venturi effect but I really don't know anything about venturis apart from some aquarium applications and having seen smoke from smouldering insulation around the outside of an air conditioning duct being sucked into the air flow within the duct and passed into the building where it eventually caused a fire alert. I'm woefully uninformed about the mechanics and effects of fluid pressure flow.
As I said at the outset, if it does work (something I'm definitely not convinced of) it has to work because it's relying on a different subset of the laws of physics to those used by traditional absorptive devices. If that's the case, then it makes no sense to say it can't work because it doesn't rely on absorption and all the reasoning for why it won't work, based on those laws applying to absorptive techniques, will be invalid because it will be relying on the wrong subset of the laws of physics.
The test of whether something works is whether you can repeatedly demonstrate the claimed results under test conditions. If it can do that, then there will be an explanation which is consistent with the laws of physics. If it can't produce the claimed results, then it doesn't work but one could then waste time arguing over whether or not the reason it doesn't work is that it doesn't comply with the theory underlying the traditional approach or because the purported theory underlying the design doesn't work. An argument can be made for either of those explanations but I would tend to opt for the second rather than the first explanation. You may have a preference for the first.
David Aiken
Follow Ups:
- Re: I was hoping some technical explanation might appear.... - Ethan Winer 10:11:24 03/08/07
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- In Reply to: Re: I was hoping some technical explanation might appear.... posted by David Aiken on March 7, 2007 at 14:27:18:
David,
MF summed it up well. If these things actually worked, they would have the same end result as absorption.
> You failed to mention that the preservation of a similar response profile to the original room would require that absorption to have exactly the same absorptive spectrum as the original room. <
No, you missed my point. If these things really did what's claimed they would not simply lower the level equally at all frequencies and leave everything else unchanged. They would reduce the decay times (what they claim), they would broaden the peak bandwidths, and they would shift the peak frequencies down a little. I see none of those.
> The test of whether something works is whether you can repeatedly demonstrate the claimed results under test conditions. <
Sure, though in this case I'd be happy to see even one legitimate test showing a positive effect on the room.
The technical descriptions that accompany the product sales pitch IMO use "new physics" explanations reminiscent of the claims made for expensive speaker cables and replacement AC power cords. Add to that waterfall graphs that either intentionally mislead, or show a basic misunderstanding of what bass traps are supposed to do.
--Ethan
- Ethan and MahlerFreak - David Aiken 19:15:06 03/08/07
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- In Reply to: Re: I was hoping some technical explanation might appear.... posted by Ethan Winer on March 8, 2007 at 10:11:24:
Don't get me wrong. I'm not arguing that these things work and I am, in fact, somewhat sceptical that they work. What I am saying is that your arguments for why they don't work simply fail the tests for logical validity.
Ethan's original claim which I took up was that they can't work because normal absorptive acoustic treatments of the same size can't produce those results. That argument fails if they work by some other method because it relies on comparing apples with oranges if the method is different.
MahlerFreak claims that the Law of Conservation of Energy can't be broken (I agree on that point) but then goes on to claim that since these panels can't do better than a perfect absorber, they can't deliver the claimed results. I'm not certain that the waterfall plots show them performing better than a perfect absorber and I agree that they can't do that. Such an argument, however, doesn't prove that they don't do what the waterfall plots claim they do.
MahlerFreak holds up a window as the perfect absorber. Let's take as an example a window 4' x 4'. It will produce 16 sabins of absorption across the full audio spectrum. Can a 4' x 4' acoustic panel produce more absorption than that? Well, it can actually produce 32 sabins over a narrower bandwidth. How? Simple, the window has only 1 absorbing surface and the panel has 2, one on each side. The effective surface area for the panel is actually the equivalent of 8' x 4' because it absorbs on both sides. That's 100% better than you can expect from a window of the same dimensions, though over a narrower bandwidth which will be determined by the properties of the material used.
We know that Helmholtz resonators provide very effective absorption over a very narrow bandwidth. There have been measurements to show that a single Coca Cola bottle can provide 5.9 Sabins absorption (if I remember correctly) over a bandwidth of a bit over .5 of a Hz. That's a stupendous amount of absorption for a small surface area, or even a small volume, whichever way you want to think of the bottle.
We know from tests that 2 small pieces of foam, each less than 1 cc in volume, can produce 20 dB or more of attenuation over a very wide bandwidth of 5or more octaves. How? If they're hearing protectors and inserted in the ear canals. Place the same 2 bits of foam in a room and you probably won't get any measurable attenuation at all. Sometimes it's not only what you use but where and how you use it.
An ASC tube trap uses a limited amount of absorptive material in a shell around an internal space. Spread that absorptive material out as a flat surface, forgoing the internal space in the process, and the absorptive power of that flat surface will not be as good as it's power when used in the tube trap. Surface area and thickness/density of absorptive material alone don't count for all of the effectiveness of a tube trap.
There's nothing magical about any of the above examples, and none of them break the laws of physics, but they each in certain circumstances and for more limited bandwidths deliver considerably more benefit that the window which is held up as the 'perfect' absorber.
Like both of you, I don't like seeing pseudo-science and glib explanations used to justify extravagent claims for a product. Apparently unlike both of you, I don't like debunking those claims with arguments that are logically invalid. That was the point I strove to make in my initial response to Ethan and I keep coming back to it.
By all means debunk spurious claims, but if you're going to do it, make sure the argument you use will actually do the job. Ethan has produced a great argument to the effect that an absorption device can't do more than an absorption device. MahlerFreak has claimed that nothing can exceed limits imposed by the Law of Conservation of Energy, but has no evidence that these devices are either exceeding, or claiming to exceed, what is permissable under that law.
Finally, as I have said many times before, proving that the explanation given for why something purportedly works is false does not prove that the thing doesn't work. People gave all sorts of explanations, all of them now accepted as wrong, for why things fall towards the earth when dropped before Newton proposed his Law of Gravity which we now accept as the foundation of the correct account. Despite the fact that their explanations were wrong, the multitude of devices which rely on gravity to work that were invented prior to Newton worked just as well when invented and explained incorrectly as they did post-Newton when we had what we regard as the correct explanation. Whatever device that actually works which we wish to talk about, there is one thing which is certain: it will work regardless of whether the explanation given for why it works is correct or not.
Can these devices produce the results shown in the waterfall plots? I don't know but the only way to find out for sure is to attempt to duplicate the measurements and to see whether or not that can be done. If they can't be duplicated, then there's a good reason to believe it can't be done. If they can be duplicated, all of the arguments anyone can dream up for why they don't work are simply wrong and irrelevant. That's my point.
I'm on the side of science. I want to see replicable results and I'd also like to have correct reasons for why things work. I'd like to see pseudo-science and fraud exposed, but I object to seeing those who claim to have science on their side claiming to have exposed something by offering proofs which fail the simple tests of logic. I've got very little science in my tertiary qualifications, and very little of that is in the physical sciences, but I do have in excess of a double major in philosophy including the equivalent of half a major in formal logic. If there is one thing that is common to all scientific proofs, it's that they are all logically valid. No one's best interests are served when the proofs or disproofs that are offered for or against something are logically flawed.
David Aiken
- Re: Ethan and MahlerFreak - MahlerFreak 16:00:33 03/09/07
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- In Reply to: Ethan and MahlerFreak posted by David Aiken on March 8, 2007 at 19:15:06:
This discussion is now well past the point of ridiculous, and I will not post again after this in hopes of getting the last word on a philosophy major :)
However, for anyone still following this thread it is worth looking at two reasons why the devices in question cannot produce the given measurements, because they illuminate some important issues in room acoustic treatments.
First, the devices in question, used as described, cannot produce anywhere close to the level of attenuation of bass seen in the graphs in any kind of real-world listening room. Second, it is impossible create a constant reduction in bass level across the frequency range in a real world room using passive devices placed as described.
To point 1: David is correct that I did not account for the two sides of the devices in question when considering the conservation of energy question. This does not double the potential effectiveness of the device, however, because if one side of the device is 100 percent effective in attenuating the sound signal, it will partially "corrupt" - attenuate - the signal reaching the opposite surface, in a way quite dependent on the frequency of the signal and the placement of the device. Nonetheless, let us make the assumption that the inventors have magically prevented this effect, and built a device capable of 100% attenuation of the signal on both front and back surfaces. Let us also make the assumption that the measurements were taken in a room fully treated as recommended - two panels in each upper room corner.
The measurements in question show a 15DB attenuation in bass frequency sound, plus or minus a fraction. Decibels are a measure of sound energy, but they are not linear measures like Miles Per Hour or similar - decibels are measured on a logarithmic scale. Thus, a 3db change in decibel measurement corresponds to a doubling or halving of sound energy. A 10 decibel reduction corresponds to a 90% reduction in sound energy, and a 15 DB reduction corresponds to approximately a 97% reduction in sound energy. In other words, for the panels to have produced the attenuation shown in the graphs, at least 97% of the bass energy in the room must impinge upon the two surfaces of the panels (assuming, again, perfect attenuation). The panels have approximately 2.5 square feet of surface area apiece, 20 square feet total. Let's generously assume that the room is very small, 12 x 10 x 8, or 592 square feet of surface area. We've agreed that a passive device cannot attenuate more energy that impinges upon its surfaces. It should be readily apparent that, even with the corner amplifying room modes, we are way short of having sufficient surface area to attenuate 97% of the sound energy in the room. An order of magnitude or more short, in fact. We could go on to calculate exactly the number of Sabins of attenuation, and therefore surface area, necessary to create a 15db reduction in overall sound pressure level in a given room, but I'm too lazy right now, and in any case the calculation is relevant only for the average sound level, due to the non-linear effects mentioned below.
This type of analysis holds true for any passive sound treatment device, and explains why you shouldn't expect large changes in bass response from small passive devices, ever.
Point 2: the graph shows a perfectly constant, within fractions of a DB, reduction in sound pressure across the measured frequency range. This is not theoretically possible to achieve using passive devices covering part of the surface of the room. The reason is that the frequency response of the speaker/room system is different at every point in the room. From a systems analysis standpoint, we would say that the speaker/room/listener system has a different, non-linear transfer function for every listener position (and speaker position, and room treatment panel position) in the room. This non-linear response occurs primarily as the result of sound waves "interfering" with each other - reinforcing each other at some points, canceling each other at others. These cancellation effects can be roughly categorized into room modes and boundary interferences, room modes occurring as the result of cancellations between waves reflected from opposing pairs of walls or corners, boundary interferences occurring as the result of reflected sound from boundaries canceling or reinforcing the direct sound from the speakers. Combined, these two categories of interferences account for most of the "shape" of the room frequency response curve, and the waterfall plots as well.
Of course, the patterns of interference, and the corresponding frequency response anomalies, will be different at every different location in the room. The passive sound cancellation device in the corner of the room "hears" a different frequency response from that "heard" at the listening position. If the panel perfectly cancels the sound it hears, it will cancel more sound at some frequencies, and less at other frequencies - and the shape of that cancellation curve will not match the shape of the non-treated frequency response curve at the listening position, and the result will be that the shape of the curve at the listening position will change. The passive treatment panel has no way to "know" what the transfer function (frequency response) at the listening position actually is, and therefore no way to create a uniform attenuation in sound level at that position.
In theory, one could approximate uniform attenuation using active devices controlled by powerful DSP engines programmed with actual room measurements at different positions. This wouldn't be particularly useful, though, because the result would be identical to applying a conventional parametric digital or analog filter over the desired frequency range - including phase shift anomalies.
The irony of all of this is that these panels, if they have any attenuating effect at all, should produce small but measurable changes in the room's frequency response curve - certainly greater changes than could be measured by switching between amplifiers or cables of similar electrical characteristics. It's just that the data currently presented doesn't allow for honest assessment of the panels' actual performance, which I am left to assume is because that performance is not particularly noteworthy.
- Re: Ethan and MahlerFreak - Ethan Winer 12:30:57 03/10/07
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- In Reply to: Re: Ethan and MahlerFreak posted by MahlerFreak on March 9, 2007 at 16:00:33:
Excellent post.
- Re: Ethan and MahlerFreak - David Aiken 22:17:51 03/10/07
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- In Reply to: Re: Ethan and MahlerFreak posted by Ethan Winer on March 10, 2007 at 12:30:57:
Let me try to restate my concerns one final time so that everyone reading this understands what we are all saying. Please feel free to correct me if I have misstated either of your positions but I don't think I have.
We all agree that the plots show a very even attenuation of sound levels across the displayed frequency range. We all agree that is a suspicious result.
You and Mahlerfreak say that such a result can not be achieved by absorption with panels of the size of these products. I agree.
The manufacturers say they aren't using absorption as the method of achieving the result. Their explanation of the technique they are using is neither detailed nor helpful in understanding what they are doing. That makes it extremely difficult to accept their explanation, which is another reason all 3 of us are suspicious.
None of the above agreed points PROVES the results are bogus. They most definitely give rise to concern but they aren't a proof that something is bogus. If you like you could regard it as circumstantial evidence that the results are bogus but that's as far as it goes. It is not direct evidence of poor testing setup and/or techniques, falsification, trickery, or something worse.
What you have both demonstrated factually, and what I never disagreed with, was that such results can not be obtained by absorption. That does not prove that they cannot be obtained by other means. You both are happy to state that you don't know of any other method to produce such effects and I accept that. I don't know of any other method either. That doesn't prove there isn't one. A proof that the results can't be achieved by absorption does not prove the products don't work by some other method and not knowing of any other method doesn't prove there isn't one. New techniques are discovered every now and then. We have no reasons on the information available to believe that these people have actually come up with a new method but we also have no evidence available to prove they haven't. The lack of information cuts both ways here. It doesn't give us any reason to believe them, but it also doesn't give us the evidence required to say with certainty that they haven't discovered another method. If you can find a bookmaker to take bets on whether or not they have, all 3 of us will be betting the same way but we don't have proof that we're right. We also wouldn't expect to lose the bet. On the information to hand, betting that there isn't a new technique involved has to be regarded as a 'safe bet', even a 'very safe bet', but it isn't up to the standard of proof.
If you want to restate all of the agreed things above and and proceed from there to a conclusion which states that you BELIEVE the results to be bogus I will accept your statement 100% and not argue one bit. That's where I stand with the proviso that I would prefer to say that I believe the results are incorrect. "Bogus" does carry an implication of fraud and it's possible that the manufacturers are sincere but mistaken. I'd prefer some hard evidence of deceit before I chose to use the word 'bogus' but that's my preference and others can choose to be less cautious given that the case for believing that the things don't work is very strong, If you want to take the very major step logically to instead claim that you have proved that the results are bogus, I must disagree. The evidence offered does not prove that. What it does, and what I have said all along, is that it gives very strong reasons (and I mean that in the strongest terms) for doubting the results.
You ask them to prove their results, and that's a valid request, and you also expect that their proof will have to measure up to reasonable scientific standards of proof. That's fine. But what I'm saying is that you should meet similar standards in your statements and one of the things that scientifically acceptable proof rests upon is logically valid arguments when inferences are drawn. Your jump from the evidence cited to your claim of proof that the results are bogus is not logically valid. I don't believe the evidence as it stands allows that jump. I think evidence of a different sort is required for that sort of conclusion, and that evidence would be things like failure to replicate the results and/or an account of their test method, the errors/mistakes made during their tests, and an account of how those errors/mistakes led to the results they claimed.
None of the three of us would not go out and buy the products on the evidence provided. None of us would recommend that anyone else went out and buy them. Where we differ, and the only place where we really differ, is that I hold back from claiming that the results are bogus because I don't believe we have evidence that proves that. What I think we have is evidence which very strongly suggests that the results shown are not accurate.
That is the point I keep trying to make. I'm not trying to deny your evidence. I'm simply trying to point out that it is not sufficient for a claim to have "PROVEN" the results are "bogus" if we're going to rely on scientific standards of proof. It may well be enough to convince readers if the standard of "proof" is one of a lack of reasonable doubt, but that's not the standard applied in science. I definitely believe that there's enough evidence for a reasonable doubt that they work. That doesn't amount to proof that they don't work.
David Aiken
- Re: Ethan and MahlerFreak - Ethan Winer 14:37:38 03/11/07
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- In Reply to: Re: Ethan and MahlerFreak posted by David Aiken on March 10, 2007 at 22:17:51:
David,
MF is doing a great job - who was that masked man? - so there's not too much more I can add. But I'll try. :-> )
> We all agree that the plots show a very even attenuation of sound levels across the displayed frequency range ... You and Mahlerfreak say that such a result can not be achieved by absorption with panels of the size of these products. I agree. <
I further argue that the only way to get results like that is to lower the volume knob. Nothing you can put into a room will have that effect. If you demolished the building so all the walls fell outward and the speakers were left standing in an empty lot, you still wouldn't get After results like that.
> What you have both demonstrated factually, and what I never disagreed with, was that such results can not be obtained by absorption. That does not prove that they cannot be obtained by other means. <
There is no way to get those results other than turning down the volume. Or maybe doing a PhotoShop job on the screen cap.
> If you want to restate all of the agreed things above <
I have restated enough times, so let's take a new approach:
Since we all agree that the results in their After graph are identical to turning down the volume, why does anybody need to buy those panels at all? Just turn down the volume. Then all those nasty room modes and peaks and ringing will be pushed below the noise floor where they won't irritate us critical listeners anymore!
> You ask them to prove their results, and that's a valid request <
Has anyone noticed that it's still only the three of us discussing this? If a thread like this were going on about my products, and I knew about it, you can be sure I'd be all over it explaining my position as best I could.
--Ethan
- See the hypothetical scenario in my response to MahlerFreak. How would you answer the questions posed? NT - David Aiken 17:39:30 03/11/07
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- In Reply to: Re: Ethan and MahlerFreak posted by Ethan Winer on March 11, 2007 at 14:37:38:
- See the hypothetical scenario in my response to MahlerFreak. How would you answer the questions posed? NT - David Aiken 17:39:30 03/11/07
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- Re: Ethan and MahlerFreak - MahlerFreak 11:46:14 03/11/07
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- In Reply to: Re: Ethan and MahlerFreak posted by David Aiken on March 10, 2007 at 22:17:51:
If anyone reading this doubts the dangers and inefficiencies created by scientific and mathematical illiteracy, this discussion should go a long way toward convincing you. Although, to be fair, inefficiencies almost always create perverse opportunities as well, without which such lucrative industries as high end speaker cable manufacturing and magical room treatment devices would greatly suffer.
There are so many flaws in David's post that it's difficult to know where to begin, but I'll simply point out that:
1. The "inference" made from the calculations I performed in my previous post is that the devices in question would have to violate conservation of energy - dramatically - in order to create the measured differences. Since David has already agreed that conservation of energy is a reasonable assumption to make, it is his argument that that draws logically invalid inferences - namely, that there is some principle of operation other than "absorption" which would allow the devices to violate conservation of energy. To be fair, it is possible that David does not recognize that inference, due to the more serious logical flaw of arguing from incomprehension of the subject at hand. Unless you can refute my very simple calculations and modeling assumptions, there is no room for "reasonable doubt" about the validity of these measurements - they are not the result of the devices as described being used as described in a realistic listening room (and note with care the contingencies in that statement, lest David come back and insist that you might create these measurements by using the devices as earmuffs, or attaching them directly to the woofers of your loudspeakers, or stuffing your head into a box constructed of these devices, or some similar bit of face-saving nonsense).
2. I never used the word "bogus" to describe the measurements. I will leave it to the reader to speculate as to the origins of these measurements, as there are many possible explanations which do not violate the laws of physics, almost all of them having to do with, umm, human factors.
Beyond this, I am bothered that my previous post describes the issue of room non-linearity in a somewhat awkward and potentially misleading way, and manages to miss an important point at that. The point becomes clearer, hopefully, by concrete example.
For simplicity, assume we have a listening room 10 feet long, constructed with very rigid walls. For the sake of this example, the other dimensions can be ignored. This 10 foot long room will have "room modes" related to the 10 foot length, room modes being patterns of cancellation and reinforcement in sound frequencies related to the 10 foot length. In this case, we will have room modes at multiples of the frequency 56.5 hertz. For instance, there will be a room mode at 113 Hertz. If we have our speakers play a 113 hertz tone at an average sound level of 100 DB, and begin measuring the sound level at various points in the room, we will discover some interesting things. For instance, at the front and back walls, the sound will actually measure louder than 100 DB. Aha! Here is proof that all of that conservation of energy stuff is BS! How can the sound be louder?! Well, because at other points in the room, it is quieter. For instance, if we measure the sound at a listening location 2.5 feet from the back wall, we will discover that the sound level is way below 100 DB. In fact, if we measure the sound at frequencies in the neighborhood of 113 hertz at that listening location, we will find that there is a sharp dip in the frequency response graph, centered at 113 hertz. This sharp dip occurs because sound reflecting from the back wall is canceled by sound of opposite polarity reflecting from the front wall, at that location, at that frequency.
Now let's introduce some sound treatment devices on our front and back walls. If these are passive devices, with no power source of their own, conservation of energy says that these devices can't create or destroy the sound energy, only transform it in some way. Part of that transformation might be from sound energy to heat, part of that transformation may be reflection of sound, some of it may be conversion into dynamic magnetic fields which interfere with the skin effect in your $12,000 speaker cables (don't worry, that last is mostly a joke, until it appears in someone's marketing brochure).
Let's assume for the sake of this example that the sound treatment devices in question are well designed passive absorbers covering much of the back and front walls, capable of absorbing most of the sound energy impinging on their front surfaces at 113 hz. Now we do some measurements again. We find that, intuitively enough, the sound level at 113 hz is significantly reduced near the back wall. Not so intuitively, as we measure the frequency response in the neighborhood of 113 hz at the listening position, we find that the dip in the frequency response graph is not as deep or sharp as before.
Why? Because our sound treatment devices have now negated much of the sound waves that reflect from the back and front wall and interfere with each other at the listening position, partially removing the non-linearity caused by the cancellation of those two waves. Although our devices absorb energy at non-modal frequencies as well, they do not absorb as much, because the sound at the boundaries is not as loud at non-modal frequencies. The serendipitous result is that a non-linearity at the front and back walls is aiding us in canceling an opposite non-linearity at the listening position, exactly what we want if more uniform frequency response is the goal.
This leads to an even more non-intuitive conclusion, easily verified with active sound cancellation devices. In order for our sound treatment devices to lower the relative 113 hz level at the listening position, they would have have to amplify the 113 hz level at the front and back walls! Passive, non-powered devices can't amplify, of course. They could be designed and physically constructed to be ineffective absorbing frequencies in a narrow band around 113 hz, thus "amplifying" 113 hz in a relative sense - but that would obviously require a priori knowledge of the room into which they were placed, and of course would be counterproductive if removing room effects is the desired goal.
What can we learn from all of this? First, every room will have non-linearities due to reflections from the room boundaries, regardless of the dimensions or shape of the room. Second, placement of devices so as to take advantage of room non-linearities is crucial - fortunately, almost all two and three wall corners work well in practice. Third, any boundary reflection energy not absorbed, or canceled by energy from powered, active devices, will continue to create some non-linearities. And finally, to the point of my previous post, it is not possible to introduce generic, passive devices into a room and achieve uniform reduction in sound energy across the frequency spectrum - not that this is desirable for accurate sound reproduction in any case.
- Re: Ethan and MahlerFreak - David Aiken 15:24:22 03/11/07
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- In Reply to: Re: Ethan and MahlerFreak posted by MahlerFreak on March 11, 2007 at 11:46:14:
Re your point 1-
The reason I said "inference" is because there is no direct evidence that the results are not genuine. The route to that determination is via reasoning rather than physical demonstration.
You said, and I agreed, that the law of energy conservation could not be broken but you then went on to hold up the open window as an example of the perfect absorber. As I pointed out, it is possible to obtain somewhat better absorption than 1 Sabin per square foot of device under some circumstances, including restricted bandwidth, from a passive device and without violating the Law of Conservation of Energy. We cannot say that there is no possible way of producing this kind of effect because we can never guarantee with 100% certainty that there isn't a way of passively producing the result. We may be pretty damn certain, even 99.99999999999999999999% certain or even a little bit more than that, but we cannot say with total accuracy what techniques will or won't be developed in the future.
All I'm saying is that without direct evidence showing that the results were not genuinely obtained, there is a logical step involved in the move from the evidence of the plots to the conclusion that they are wrong. That step is inferential.
Your point 2: Ethan used the word 'bogus'.
Let's set up a different scenario as a hypothetical and ask some questions.The scenario: It is some months BEFORE Manfred Schroeder publishes the results of his experiments on generating acoustic diffusion using diffraction gratings. These results lead to the eventual development of diffusors based on mathematical models. At the time we are talking about, some months before publication, the only methods of diffusion in use involve curved surfaces like polycyndrical reflectors.
Hypothetical question 1: Somebody tells you it is possible to produce more effective diffusion than is currently achievable by using an array of staggered well depths. Do you believe them or do you say it can't be done because there is no known method or theory which indicates that this is possible? Remember, there is at this point in time no published material on this technique from any source.
Hypothetical question 2: It is now some months later and you have just come across Schroeder's claims but Schroeder is not a researcher at respectable institutions. Instead he is the principal of a small company selling acoustic treatments and the claims are contained in advertisements for a new product, a quadratic residue diffusor. Photos of the device with claims of its effectiveness are contained in the advertisement but no scientific account is given. No scientific account of the device has yet appeared in the professional scientific literature. Do you believe the claims of the advertisement or do you respond in a similar way to the way you would respond to hypothetical question 1 above.
Hypothetical question 3: The events described in question 2 have not occurred. Instead what has happened is what happened historically. Schroeder is a scientific researcher working at respectable institutions and he publishes his study and theories in the professional scientific manner and you read them in a peer- reviewed scientific journal or hear them in a presentation at a scientific conference on acoustics. A full theoretical and mathematical explanation/description is given along with detailed test description to enable others to repeat the experiments reported. Would you respond differently to reading the claims in this way than you would if you came across them in the manner outlined in question 2 above?
Now, to give my honest answers as to how I reply to those questions:
Question 1: I would not be inclined to accept the claims on the basis that they did not conform to my knowledge base.
Question 2: my response would be very similar to my response to question 1, plus I would have doubts as to the honesty and reliability of the person/company making the claims. I would be highly suspicious of any test results shown.
Question 3: I would take the claims a lot more seriously than I took the claims in the first 2 scenarios. I may not yet accept them but I would be inclined to give them a lot more credence and, if I did not accept them on the basis of the initial published account, I would accept them on evidence of the replication of the results by equally reputable researchers.
Note that in all 3 cases we're talking about the same device and it is effective and does not violate any scientific principles. The only differences in the examples are the timing of the claims and the way in which they come to your attention. It is impossible to prove in scenarios 1 and 2 that the devices don't work because they actually do work. It is possible to give reasoned responses explaining why they can't possibly work that will convince many people that they don't, but that reasoning will be wrong and no-one really KNOWS that they don't work, they simply believe that they can't work and mistakenly accept that belief as knowledge.
If these devices do work, we're currently in circumstances similar to those in my first 2 questions. Extreme scepticism is justified and the answers I gave above as my response to my first 2 questions are appropriate responses at those times and in those circumstances, given the level of my knowledge and the lack of published accounts from reputable sources.
Correctly observing that there is no way currently known of producing a particular effect does not guarantee that it cannot be done.
We are required to leave open the possibility that our current circumstances are those of my second scenario and that someone at some time in the future will publish an account that explains the effect to our satisfaction and the technique becomes accepted even though it is radically different to previous approaches as diffusion by the technique discovered by Schroeder radically differed from earlier diffusion techniques.
Do I think this is going to happen here? No I don't, but at least I'm honest enough to admit that I would say exactly the same thing in response to my second scenario. I'm also old enough to know that in the past I have made judgements I considered absolutely correct on what at the time I considered was impeccable evidence, only to be later proven wrong. I'm also prepared to admit that I may do so again in the future. On something like these devices I'm prepared to be as sceptical as I can be but without actual direct evidence demonstrating how the claimed results were wrongly obtained, I'm not prepared to claim that I KNOW they are false and that they are impossible.
David Aiken
- Re: Ethan and MahlerFreak - MahlerFreak 21:26:12 03/11/07
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- In Reply to: Re: Ethan and MahlerFreak posted by David Aiken on March 11, 2007 at 15:24:22:
"As I pointed out, it is possible to obtain somewhat better absorption than 1 Sabin per square foot of device under some circumstances, including restricted bandwidth, from a passive device and without violating the Law of Conservation of Energy. We cannot say that there is no possible way of producing this kind of effect because we can never guarantee with 100% certainty that there isn't a way of passively producing the result."
Wrong. What you pointed out is that panels have two sides, and so that doubles the surface area of the panel. You did not point out that panels can have more than 1 sabin per square foot, for the simple reason that they can't, without violating conservation of energy. Bad logic!
"All I'm saying is that without direct evidence showing that the results were not genuinely obtained, there is a logical step involved in the move from the evidence of the plots to the conclusion that they are wrong. That step is inferential."
Well, I don't have the benefits of a philosophy education, so I can't say what a valid inference is or not. All I can say is that some possibilities can be excluded without resort to experimentation. For instance, I can exclude the possibility of powering our electrical grid through perpetual motion machines - and perpetual motion is impossible for precisely the reasons that the results in question are impossible, namely conservation of energy.
To your hypothetical questions, the answer is that of course I would be more likely to credit theories advanced by researchers with a track record. But your straw man is a logical non-sequiter: you are attempting to counter a quantitative argument with a sociological and psychological one. It is as though you were arguing that because at one time people were skeptical of ever building a practical aviation jet engine, we should now be prepared to reject calculations showing that you can't fly a 747 using a Briggs and Stratton lawn mower engine. The argument I made is a quantitative argument, which demonstrates that removing 97% percent of a room's broadband sound energy using passive devices representing 3% percent of the room's surface area violates conservation of energy. No amount of logic, philosophy, sociology, psychology, or random assertion will counter that argument - only an analysis which shows errors of very large quantitative significance in assumptions or calculations.
And BTW, if you really want to counter the essentially Newtonian notion of conservation of energy, why not resort resort to relativity and quantum mechanics? For instance, the measured results are feasible if the devices in question uniformly transform the space in the room such that 97% of the sound energy is converted to matter. This is truly a Nobel prize winner, to say the very least. Of course, if this is the sort of possibility that you consider reasonable, it says more about your credulity than about the scientific credibility of these devices ...
I have the same reaction as Ethan - why aren't the inventors of this device here defending their data, if only to throw enough BS to protect that significant segment of their potential market with big wallets and small understanding of science?
- Re: Ethan and MahlerFreak - David Aiken 23:45:46 03/11/07
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- In Reply to: Re: Ethan and MahlerFreak posted by MahlerFreak on March 11, 2007 at 21:26:12:
You said: "To your hypothetical questions, the answer is that of course I would be more likely to credit theories advanced by researchers with a track record. But your straw man is a logical non-sequiter: you are attempting to counter a quantitative argument with a sociological and psychological one. It is as though you were arguing that because at one time people were skeptical of ever building a practical aviation jet engine, we should now be prepared to reject calculations showing that you can't fly a 747 using a Briggs and Stratton lawn mower engine. The argument I made is a quantitative argument, which demonstrates that removing 97% percent of a room's broadband sound energy using passive devices representing 3% percent of the room's surface area violates conservation of energy. No amount of logic, philosophy, sociology, psychology, or random assertion will counter that argument - only an analysis which shows errors of very large quantitative significance in assumptions or calculations."
I haven't suggested anything like rejecting calculations that show you can't fly a 747 using a lawn mower engine. I haven't argued that you could remove 97% of the room's broadband surface energy using passive devices representing 3% of the room's surface area.
I also haven't argued that these devices can produce the results shown in the waterfall plots.
We don't have any acceptable or plausible evidence for what they can do. We have no evidence that they do absolutely nothing and if we claim they don't work, we're essentially saying that they either do nothing or do so little as to be of no value to the user. I'm saying that we need evidence to show that they either do nothing or do so little to be of no practical value before we say that they don't work. Nothing you or Ethan has said goes to that point.
I don't dispute your reservations. I share them. I simply don't think they support the categorical 'don't work' pronouncement that Ethan made and which I originally responded to. I think we need something else apart from the points raised by both of you in reservation before we can make such a claim ourselves. We don't have proof that they don't work. We have good scientific reason for asserting that they don't do what they claim. That isn't the same thing.
The point of the questions in my hypothetical scenarios was simply to show that we could be presented with claims about a product, even accurate claims about a product, and still be justified in holding strong doubts about the product because of the way in which the claims were presented and the state of our knowledge of acoustic technology at the time. We are justified in extreme scepticism in response to questions 1 and 2 in my view, and what we would want to see is test results showing what the product actually did. That's what we need here as well. Yes, there is a difference between this case and the case in my question 2, and that difference is that we know that Schroeder style diffusors work and, in question 2 I didn't suggest that any of the claims made for the diffusor exceeded what it could actually deliver. Even so, based on the amount of knowledge I indicated that you would have when you made your judgement in question 2, I think that all of us would probably have believed that accurate claims for what such a diffusor could deliver would have been unrealistic and implausible. We definitely believe the claims in this case to be unrealistic and implausible.
If you say that you would have been sceptical about the claims in question 2 and you are sceptical about the claims here, but you know you can't be wrong here, then what difference between the scenario in question 2 and the circumstances in regard to the product we're discussing allow you to absolutely guarantee that you can't be wrong here? Let's allow that the claims being made by the manufacturer in this case are excessive and can't possibly be demonstrated. That still doesn't prove that the product doesn't work. If a manufacturer wants to claim that their speaker produces 250 dB output at 1 metre for 1 watt input using certain drivers and we know from the drivers specifications that such a output is impossible, does that prove that the speaker doesn't work? The speaker works if it only produces 80 dB at 1 metre for that input or even only 40 dB for that matter but it definitely doesn't work as claimed. How do you prove that the speaker actually doesn't work? You need tests which prove that it doesn't produce anything.
We've got the equivalent of 250 dB claims and driver specs that demonstrate that nothing like 250 dB can be generated. We don't have evidence of what the thing does, so we don't know whether it fails to work at all, does so little as not to be of any practical value, or does something that would help but nothing at all like what was claimed. We aren't in a position to say they don't work.
David Aiken
- Re: Ethan and MahlerFreak - Champion 01:11:48 03/12/07
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- In Reply to: Re: Ethan and MahlerFreak posted by David Aiken on March 11, 2007 at 23:45:46:
David, I don't think MF or Ethan has ever suggested that the device do nothing at all, just that it can't be that effective and it is highly unlikely that it will do anything significant with the size of the panel. I am sure putting anything in the room will has some effect acoustically, but whether it work as well as claimed is a different question.
I don't have a degree in philosophy and I have little knowledge on acoustics comparing to any of you guys. But to me, if the manufacturer make a claim about the performance of a product that is almost impossible to achieve (with the current knowledge of science), and does not give a hint about how it can be done, then I have no reason to believe that it works. And how do you define 'work'? Well, to me, it 'works' if it perform as expected and meet the specifications. If it does not meet the specifications, then it does not work.
Sure, strictly speaking, we cannot prove that the device does not work. Actually, we cannot prove anything wrong at all with 100% confidence. But if you go down that track then any discussion becomes meaningless. A manufacturer may claim that if you shine light on to his newly designed panel, then the sound will get absorbed whereever the reflect light reaches and 'publishes' the result. Can you proved that it is wrong without going to his lab and try it? I can't but I think it is his responsibility to prove that it is right. That is how science work. A claim is wrong if it violates the rules that we currently know of, until you can prove that it is right.
- An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious - David Aiken 14:58:33 03/12/07
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- In Reply to: Re: Ethan and MahlerFreak posted by Champion on March 12, 2007 at 01:11:48:
You may be right that neither has said they don't work. I've come to think that this thread has become more and more confused as it has proceeded, something I have to accept part of the responsibility for, and it has definitely run its term. I'm not even going to bother going back over it in order to confirm in detail what or wasn't said or by whom.
I originally joined in simply to make one point. Ethan made a claim that they couldn't do what they claimed because you couldn't get those results with absorption. I wanted to make the point that proving something couldn't be done with absorption didn't mean it couldn't be done by some other means and that the devices claimed to use a different means.
From there, Ethan and MahlerFreak started providing reasons why the difference between the before and after plots couldn't be obtained by any means. Those arguments are certainly compelling and I don't disagree with them, but I tended to obsess about my original point that proving that technique A doesn't work does not prove that technique B doesn't work, picking up on further statements they made which I felt were overly generalised and skimmed over genuine exceptions, plus responding to several misinterpretations of my position by them. I still wonder whether they actually believe I think these things can produce the results displayed by utilising some 'magic' method. I don't and never have. Anything they actually do has to be done by mechanisms that work according to the laws of physics.
My only qualification to that point is that our understanding of those laws is currently imperfect, will remain so indefinitely, and that some of our advances in science make us realise that what we believed about one or more of those laws was wrong to some degree. I'm not suggesting that happens often or that it is the case here. I'm simply saying that we're not infallible and I don't like seeing statements made in terms I regard as too absolute, especially when they're made in the context of debunking something. It's one thing to point out the flaws in someone else's claims but I do think that when you do so, you should do your best to ensure that there aren't obvious logical flaws in your arguments. An invalid argument proves nothing and an invalid argument which attempts to show that something doesn't work or doesn't do what is claimed can actually weaken your position. I don't like seeing people who are saying things I am in broad agreement with doing what I regard as shooting themselves in the foot while doing so. I'd rather see them present a slightly more limited rebuttal that holds up against all objections.
I don't agree with you that we can't prove anything at all with 100% confidence. We can definitely prove some things with 100% confidence. We can prove that aircraft do fly, or to put it more precisely, that flight in heavier than air vehicles is possible and we can prove that with 100% confidence. They're doing it and that's all the proof required. I don't think it's usually particularly difficult to prove that those things which do work actually do work. It's not too difficult, either, to prove that something that doesn't work actually doesn't work. Where things do get difficult is when we try to prove that a particular something absolutely can't work or doesn't exist or the like. Negatives are particularly hard to prove because testing doesn't go far enough on it's own. All a given test proves is that the thing didn't work under those conditions and that result can't be generalised to a can't work under any conditions conclusion. That's the original point I was attempting to make with Ethan back again. I am reluctant to believe that we can ever prove with 100% certainty that something won't work or doesn't exist, but we don't need an absolute 100% certainty for most things in life.
While I do have a limited background in some science related areas, largely health related rather than 'hard science' like physics, my main tertiary qualification is in philosophy including a healthy dose of formal logic. That background does put a different spin on your understanding of the word "know" and what is entailed if you claim to know something. That is the basis of my original reservation and I was trying to make some of what is entailed a little clearer with my hypothetical scenario about Schroeder style diffusors but MahlerFreak simply missed the point there and regarded me as setting up a straw man. I wasn't. The point was that if you claim to know something that is subsequently proven wrong, then you really didn't know it. You held an extremely strong belief in it. I was trying to give an example of a situation in which a person would be tempted to say that they 'knew' something couldn't work but would subsequently would be proven wrong and to do so with something where neither Ethan or MahlerFreak would want to argue about the science involved, something where the only difference in the variations on the scenario was the amount of information you had in your possession when you had to make your judgement, and where the variations about the amount of knowledge you had were both plausible and relevant to the discussion in this thread. I think I came up with a good hypothetical but I don't seem to have made the point. I think there was just too much heat in the discussion by that stage.
Anyway that's my take on the whole sorry saga and I think it's definitely best that we all draw it to an end at this point. I don't think any of us have presented our best points at various stages here, and we've all been a bit too eager to nitpick on detail and stray from a couple of genuine and quite serious points of principle by confusing measurable aspects relating to a given product and general principles about what sort of general claims can and can't be supported by certain sorts of evidence. As I said at the outset, I have to accept part of the responsibility for that, for which I apologise. I should probably try to keep my contributions here to the practical things, something Ethan and I rarely disagree on as many past threads in which we've both contributed, will show.
David Aiken
- Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious - MahlerFreak 19:41:29 03/13/07
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- In Reply to: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious posted by David Aiken on March 12, 2007 at 14:58:33:
David,
I've been out of town, helping my parents with a medical crisis, which largely explains both my lack of response the last two days and the free time I had in the previous days to engage in this discussion.
I find significant parts of your last two posts to be inconsistent with your posts preceding - and I'm much more in agreement with the latest posts. In the spirit of your last post, it would be quite uncharitable, and unproductive, for me to be particular on this point.
I certainly agree that progress is often made by those who choose to ignore the judgments of those who equate "impossible" with "improbable" or "beyond my imagination". My own career is sufficient evidence to prove this to me. At the same time, the concept of "impossible" is extremely useful even when it means "improbable to a very high degree of certainty". This explains why, although I certainly fit the profile of an audiophile - judged by my expenditures of passion, time, and money over 25 years of adult life - I am often despairing of the high-end audio industry overall.
I was not joking about the perverse incentives underpinning high-end audio. Given the inherently subjective, psychoacoustical nature of listening to reproduced sound, the temptation to appeal to psychological factors is a powerful factor for any audio reproduction business. Given the superficially rational, scientific basis of the societies most able to afford high-end audio products, it is no surprise that high-end audio businesses will attempt to justify claims of significant subjective improvements through scientific theories and experiments - whether or not there is real science behind the product.
And even when the science is real, the potential subjective impact is often greatly exaggerated - the real differences in physical sound pressure arriving at a listener's ears due to electronic and cable changes may be far less than moving the listener's head a couple of inches, for instance. (Note for fellow audiophiles - I did not say amplifiers and cables "sound the same". But: treating my ceiling with RPG diffusors, in conjunction with a number of other room treatments, created a very dramatic measurable and audible difference in sound, that I might describe as "tubes on steroids").So what? If the consumer is happy, who cares whether the happiness is due mostly to real or illusory differences? Well, you should. Real differences are more likely to matter to a broad range of consumers, while purely subjective difference are, by definition, personal. Any experienced high-end listener who's taken the time to do the comparison carefully recognizes that 128 kbps compressed audio does not have the same subjective quality of sound as CD (to say nothing of the high-resolution formats). But how will we marshal the credibility to convince the many millions of iTunes customers of this, when we are associated with an industry which systematically obfuscates and exaggerates both the scientific and subjective benefits of its products?
The product we've been discussing is being marketed in exactly the worst possible way, from my perspective, in that it is represented as creating differences which are quantitatively impossible by universally accepted scientific principles, and furthermore undesirable even if they were true! And as I was careful to point out, the product may indeed "work", but not much better, and possibly much worse, than passive products of similar physical dimension.
The high end audio industry often laments its failure to create broader based appeal. I would suggest that this failure is intrinsic to the industry as currently structured - much of it DEPENDS on the narrow appeal it has to listeners for whom subjective experience is substantially disconnected from physical reality. And yet, the best the industry has to offer is subjectively extraordinary to a very broad audience. By holding the industry to the highest scientific standards, we ultimately encourage the development of solutions of appeal to both perfectionists and "ordinary" consumers.
And now it's time for me to terminate my participation in this discussion, and go listen to the Brahms 3rd, or Sibelius 6th, or Shostakovich 4th, or Mahler 7th, or any number of other works which I know will make me happy without resort to scientific analysis :)
- Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious - David Aiken 20:39:42 03/13/07
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- In Reply to: Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious posted by MahlerFreak on March 13, 2007 at 19:41:29:
"I find significant parts of your last two posts to be inconsistent with your posts preceding…"
Well, the difference was that I started out with a point I wanted to make, then got progressively more distant from that point, before finally trying to get back to it at the end. I don't think I was inconsistent but I certainly got lost on some of the points, and ended up trying to prove the point I wanted to make from some things that weren't appropriate for that sort of proof. In other words, I ended up doing what I started criticising Ethan of doing and I ended up shooting myself in the foot on a couple of points as a result.
Note: the following remarks ARE NOT related to acoustical or logical issues:
- Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious - Ethan Winer 14:54:13 03/14/07
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- In Reply to: Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious posted by David Aiken on March 13, 2007 at 20:39:42:
Guys,
I've been too busy to reply much lately either.
> I am interested in whether something actually does something or not because there's no point in spending money on something that does nothing <
Exactly.
> I do think that knowing how something works is important. <
Me too.
So I assume we can now conclude that the panels in question probably do not really have the effect shown in the waterfall plots, yes?
And by extension I assume we can further conclude that were there anything to those waterfall graphs, someone from the company would have chimed in by now to explain what we're overlooking.
Hey, that works for me.
--Ethan
- :-((((((((( - David Aiken 15:57:14 03/14/07
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- In Reply to: Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious posted by Ethan Winer on March 14, 2007 at 14:54:13:
"So I assume we can now conclude that the panels in question probably do not really have the effect shown in the waterfall plots, yes?"
Well, we can assume that for those of us who participated in the thread. I wouldn't bet that everyone who didn't participate, including the many who didn't even see it, would agree with you.
"And by extension I assume we can further conclude that were there anything to those waterfall graphs, someone from the company would have chimed in by now to explain what we're overlooking."No, we can't assume that. The company may be blissfully unaware of this whole thread.
Stop being wicked! :-)
David Aiken
- Re: :-((((((((( - Ethan Winer 10:54:02 03/15/07
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- In Reply to: :-((((((((( posted by David Aiken on March 14, 2007 at 15:57:14:
David,
> The company may be blissfully unaware of this whole thread. <
Unlikely given that the Robo guy in the Tweaks section saw this thread move to here. At least I assume that "Robo" is from that company. If you want to be sure they see it and have a chance to chime in, please invite them here. Personally, I'd love to hear their explanation.
Really, David, I think this has gone about as far as it can. I use ETF all the time, and as I said much earlier in this thread, the Before and After graphs shown are unlike any ETF graphs I've ever seen.
--Ethan
- Re: :-((((((((( - David Aiken 17:42:55 03/15/07
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- In Reply to: Re: :-((((((((( posted by Ethan Winer on March 15, 2007 at 10:54:02:
Ethan,
How about I don't invite them.
Given what we did to this thread without them here, I hate to think what we could do to a thread with them here.
David Aiken
- Re: :-((((((((( - David Aiken 17:42:55 03/15/07
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- Re: :-((((((((( - Ethan Winer 10:54:02 03/15/07
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- :-((((((((( - David Aiken 15:57:14 03/14/07
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- Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious - Ethan Winer 14:54:13 03/14/07
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- Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious - David Aiken 20:39:42 03/13/07
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- Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious - LarryB 17:47:08 03/13/07
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- In Reply to: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious posted by David Aiken on March 12, 2007 at 14:58:33:
David's arguments are, in essence, an eloquent restatement of what is perhaps the most important lesson I learned in graduate school: "Absence of proof is not the same as proof of absence."
By the way, I enjoyed this thread immensely. Seriously.
Larry
- Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious - Ethan Winer 14:56:25 03/14/07
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- In Reply to: Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious posted by LarryB on March 13, 2007 at 17:47:08:
Larry,
> "Absence of proof is not the same as proof of absence." <
Great point, and that has ramifications far beyond audiophilia.
But this does not mean that every conceivable crackpot theory deserves consideration solely because it cannot be proven false.
--Ethan
- "Absence of proof is not…" states it a lot faster and better than I did. NT - David Aiken 19:58:07 03/13/07
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- In Reply to: Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious posted by LarryB on March 13, 2007 at 17:47:08:
- It's a good thing I don't get paid by the word - LarryB 08:18:06 03/14/07
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- In Reply to: "Absence of proof is not…" states it a lot faster and better than I did. NT posted by David Aiken on March 13, 2007 at 19:58:07:
:) :)
- It's a good thing I don't get paid by the word - LarryB 08:18:06 03/14/07
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- Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious - Ethan Winer 14:56:25 03/14/07
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- Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious - Champion 16:05:33 03/12/07
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- In Reply to: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious posted by David Aiken on March 12, 2007 at 14:58:33:
Hi David, I understand what you are trying to get at and it did make me think. I don't think you need to apologize. This is one of the very rare threads on AA that have gone this far and everyone is still saying things that make sense and do not just attack each other!!! And I am sure those who had follow the discussion actually learn alot, esp. with the detailed explanation from MF and Ethan.
'something Ethan and I rarely disagree on as many past threads in which we've both contributed'
I agree. And yes, you guys are great and that's why nowadays I tends to stick to this forum to learn rather than going to other forums on AA!!!
- Re: An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious - MahlerFreak 19:41:29 03/13/07
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- An explanation/apology/conclusion to this thread? - caution: somewhat long but hopefully non-contentious - David Aiken 14:58:33 03/12/07
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- Re: Ethan and MahlerFreak - Champion 01:11:48 03/12/07
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- Re: Ethan and MahlerFreak - David Aiken 23:45:46 03/11/07
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- Re: Ethan and MahlerFreak - MahlerFreak 21:26:12 03/11/07
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- Re: Ethan and MahlerFreak - David Aiken 15:24:22 03/11/07
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- Re: Ethan and MahlerFreak - Ethan Winer 14:37:38 03/11/07
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- Re: Ethan and MahlerFreak - David Aiken 22:17:51 03/10/07
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- Re: Ethan and MahlerFreak - Ethan Winer 12:30:57 03/10/07
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- Re: Ethan and MahlerFreak - Ethan Winer 14:53:31 03/09/07
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- In Reply to: Ethan and MahlerFreak posted by David Aiken on March 8, 2007 at 19:15:06:
David,
> Ethan's ... argument fails if they work by some other method because it relies on comparing apples with oranges if the method is different. <
No, because:
> MahlerFreak claims ... these panels can't do better than a perfect absorber <
Which is irrefutable.
> Such an argument, however, doesn't prove that they don't do what the waterfall plots claim they do. <
David, those waterfall plots are totally bogus. I'm sorry if you don't understand that, but I've explained why twice so far now.
> the window has only 1 absorbing surface and the panel has 2, one on each side. <
Okay, but the Cathedral Panels are mounted flat on a wall. Even if they were mounted out in the room so they had twice as many sabins of absorption, they're still way too small to do what's claimed. And then they wouldn't be close enough to corners to have much effect at bass frequencies.
> There have been measurements to show that a single Coca Cola bottle can provide 5.9 Sabins absorption (if I remember correctly) over a bandwidth of a bit over .5 of a Hz. <
When you stuff the bottle with insulation to broaden the bandwidth, the absorption at each frequency goes down. These magic panels claim to absorb 100 percent over the full 20-200 Hz range on that ETF graph. Again, this is "new physics" in spades.
> If they're hearing protectors and inserted in the ear canals. <
You're really stretching it pal!
> Surface area and thickness/density of absorptive material alone don't count for all of the effectiveness of a tube trap. <
Yes it does.
> proving that the explanation given for why something purportedly works is false does not prove that the thing doesn't work. <
I can't prove the Easter Bunny doesn't exist either, but that doesn't mean it's likely to exist. In this case the burden of proof is squarely on the vendor, and if those ETF graphs are the best they've got, they have proven nothing other than they don't understand how to use ETF. But it goes further than that because ETF will not produce Before and After graphs like those without a little sleight of hand.
> the only way to find out for sure is to attempt to duplicate the measurements and to see whether or not that can be done. <
You do that and let me know what happens, okay? :-> ) For now I'm quite satisfied.
--Ethan
- Re: Ethan and MahlerFreak - MahlerFreak 16:00:33 03/09/07
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- Ethan and MahlerFreak - David Aiken 19:15:06 03/08/07
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- Re: I was hoping some technical explanation might appear.... - MahlerFreak 15:35:34 03/07/07
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- In Reply to: Re: I was hoping some technical explanation might appear.... posted by David Aiken on March 7, 2007 at 14:27:18:
The venturi effect is the very well known effect that fluid flowing along a boundary will cause a pressure reduction near that boundary - it is fundamental to the operation of an engine carburetor, for instance. It is very difficult for me to see how a passive device, placed in the corner of a room, could generate substantial airflow velocities parallel to the boundary itself (the direction of flow that would be necessary to cancel pressure at the boundary).
But that is beside the point. Regardless of the theory of operation, these are passive devices - they aren't "powered", except by the sound energy which impinges on them. A perfectly efficient passive device can capture, at most, precisely enough sound energy to cancel the pressure waves which impinge on it's surface. In other words, if they are perfectly efficient at converting sound energy to heat (absorption), or perfectly efficient at converting sound energy into it's negative, or some combination, they will act identically to holes in the wall of the size of the panels themselves. No principle of operation can allow these panels to dissipate more energy than impinges on their surfaces - such a principle of operation would violate conservation of energy, and earn its inventors Nobel prizes, not to mention solving the oil crisis.
Now, a powered device of modest size can be whole different animal, but that's off the subject at hand.
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