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Greetings fellow free reed enthusiasts,

In another thread, I made the following suggestion, and perhaps it's worth including it in its own thread.

 

 

As an aside, this result suggests a very interesting experiment that concertina reed makers might want to try. Make two different tongues of different materials (say steel and brass), with constant cross sectional area and having the same length and the same parameter E*(a^2)/Rho. According to these theoretical considerations, both tongues should produce the same acoustic sound: fundamental plus overtones. My feeling is that, if this conclusion can be experimentally verified, our understanding of the free reed would be significantly increased.

 

 

In the above, E is Young's Modulus, a is tongue thickness, and Rho is material density. The simplest example would be a tongue with constant cross section vs. axial length: no taper and no profiling. I believe the criteria here apply also to cases of taper and profiling, as long as their axial dependencies are the same for both tongues, but I'd first like to look at the corresponding solution to the wave equation before asserting that here.

 

Best regards,

Tom

www.bluesbox.biz

 

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Different tongue material sound different, if one makes reeds with the same dimensions and stiffness. Material density varies. Do tests your self. I have made reeds from different material in the past.

Youngs modul is in reality a shaped curve an not a exactly equal shaped line on on different Material:

http://www.setareh.arch.vt.edu/safas/007_fdmtl_24_youngs_modulus.html

Material Density Rho is cant be the same for different Materials:

https://en.wikipedia.org/wiki/Density

So to make a reed sound on the same pitch you maust change the dimensions or the taper or profiling or all together.

 

But there are alt of other criteria to make a reed sound different. A lot of people wat to make reeds sound as reeds sound in old Instruments but relay we will never succeed.

Every reed set has its own individual character. That may be very close in sound to other but never exactly the same. There is fa to less modern testing on the subject.

Best regards Johann

Edited by Johann

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Hello Tom and Johann

I could do this but not until at least June.

I have never seen/heard what I would call a quality brass reed ie. one with excellent clearance between reed and frame. Consequently when people say brass reeds sound different to steel I wonder if it is a quality difference we are hearing more than or as much as an intrinsic material difference. This is similar to the argument "later Wheatstones are not as good as early ones. Later Wheatstones have aluminium reed frames. Aluminium frames are not as good". So while the test would need to be simple in order to get done can I suggest the clearance between tongue and frame would need to be consistent across both examples?

If brass reeds were to create a different and warmer sound than steel then it will be for a specific scientific reason, not because they are honey coloured. My guess is they would have a different stiffness and for this reason it would be interesting to be able to measure the tip speed of the reeds. This might not need fancy equipment, maximum tip height above the frame could be used in conjunction with hertz to calculate a speed. This would mean we could see if any difference in higher partials and consequent tone might be explained by tip speed.

The time involved to create the steel reed assembly would not be great, but sourcing brass at the right hardness would be an issue, starting with an ignorance of what that hardness might ideally be and even how it is measured in brass. So, a few questions ; does banging it with a hammer to work harden it only create a zone of surface hardness? What happens when you file it to create a profile, does it lose its hardness on the top? All of the brass I have here is "free machining", ie. includes a small percentage of lead. Can this be used? Does anyone have a working comparative knowledge of steel and brass profiles? Would brass and steel deliver the same pitch for the same physical profile and length and width dimensions? So many questions...

An afterthought, perhaps the thing to do would be to get a brass reed assembly and copy it in steel.

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I have never seen/heard what I would call a quality brass reed ie. one with excellent clearance between reed and frame.

 

Chris--

 

I think I've heard that Wheatstone made high-end brass-reeded concertinas that presumably had reeds of this quality, but I don't think I've ever seen one myself.

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This is similar to the argument "later Wheatstones are not as good as early ones. Later Wheatstones have aluminium reed frames. Aluminium frames are not as good". So while the test would need to be simple in order to get done can I suggest the clearance between tongue and frame would need to be consistent across both examples?

 

If brass reeds were to create a different and warmer sound than steel then it will be for a specific scientific reason, not because they are honey coloured. My guess is they would have a different stiffness and for this reason it would be interesting to be able to measure the tip speed of the reeds. This might not need fancy equipment, maximum tip height above the frame could be used in conjunction with hertz to calculate a speed. This would mean we could see if any difference in higher partials and consequent tone might be explained by tip speed.

 

The time involved to create the steel reed assembly would not be great, but sourcing brass at the right hardness would be an issue, starting with an ignorance of what that hardness might ideally be and even how it is measured in brass. So, a few questions ; does banging it with a hammer to work harden it only create a zone of surface hardness? What happens when you file it to create a profile, does it lose its hardness on the top? All of the brass I have here is "free machining", ie. includes a small percentage of lead. Can this be used? Does anyone have a working comparative knowledge of steel and brass profiles? Would brass and steel deliver the same pitch for the same physical profile and length and width dimensions? So many questions...

 

These are all excellent and well-thought considerations. Another may be that steel manufacturing, while an ancient craft, underwent constant changes from 1870-1920 in the UK. Despite advances in manufacturing in the US, the british model for steel production was un-matched for high-end, top quality material. This raises many more questions than it answers, i.e: What properties were desired by reed-makers? How much stock did they purchase per order? Where did they source their material?

Per brass manufacturing, the material itself was less crucial to armament manufacturing, the one exception being cannon and/or naval armaments. The only reason I mention weapon manufacturing is that this may be the best-documented source for steel and brass production in the era. It may, however, be of little use in regards to the concertina.

The last thing that I will mention will be machines. While the UK excelled in brass and steel production, by 1920, American machining was far ahead of anything in the world and the British were well aware of this, being their main competitor. I would imagine that UK reed-makers were employing American machinery (from rollers to shears) and high-end British steel to manufacture their reed tongues. This is largely a guess, on my part, as to why 1920s concertinas are considered the 'high-water-mark' of reed quality.

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I have had two Aeolas with brass reeds, they were for export for the tropics. One was ebony ended the other metal. They were both excellent concertinas , so good that experienced players were deceived by trying to guess what the reed material was.

Regards.

Mike Acott

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First i would not think reed maker did use especially made steel or Bronce Alloys for reeds. Best source for reeds war clock springs. Think also abut it that a lot of reed makers war mechanics that war clock maker as well. Bronce Alloys was the usual stuff that ware in use for Years for Cannons. Best regards Johann

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I have both played and worked on a few high end brass reed tongued instruments, They are very good, not so loud but the trebles are responsive. The baritones can be a bit slower to respond but are very mellow. My experiences support Mike.

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I apologize for this delayed response to the many interesting comments in this thread I started. I’ve been going out of town and tending to important issues. For those who don’t know, I’m in Complete Response for Multiple Myeloma, a cancer of the plasma cells in the bone marrow. I have medical treatments (infusions) two days of every other week, and they give me headaches and hangover, but I’m not complaining, it’s not too bad. If by chance, anyone else in the group is going through the same thing, I invite you to contact me privately and we can compare notes, even though this disease is extremely variable.

 

Now being able to provide a more energetic description, I must first state clearly that the suggestion I proposed in the OP is really only the simplest theoretical step in trying to understand why different tongue materials might produce different acoustic effects, and I want to correct a sentence in the “Quote” part of that post, which was a misstatement:

 

According to these theoretical considerations, both tongues should produce the same acoustic sound vibration: fundamental plus overtones.

 

The Euler-Bernoulli wave equation for a vibrating bar is the simplest formulation for such behavior, and it is considered very accurate when rotational inertia and translational shear can be neglected, and that is the case if the thickness of the bar is not too great and the vibrations contain only small angles, which often occurs with free reed tongue vibration.

 

Attached is a .docx file that gives the E-B bar equation and the Timoshenko bar equation. I was not permitted to upload this file. Anyone?

 

Shown is the simplest form for the E-B bar equation, which does not include a forcing function (external force, such as a bellow’s pressure), nor aerodynamic drag (friction) terms. Mathematically, it is called a non-dissipative (frictionless), homogeneous formulation, and the utility of it is that it (along with its boundary conditions) provides the eigenfunctions for any type of bar vibration consistent with its underlying simplifications. In other words, the complete solution when you do include a forcing function with friction (the complete formulation) is made up of these same eigenfunctions, which give the axial dependence of the shape of the bar (its curve). The time dependence of the vibration in this complete case is then determined by the time dependency of the forcing function with the complete formulation.

 

Thus, the simple suggestion in my OP will reliably predict accurate frequencies and general axial beam shapes for the fundamental and overtones that are experienced in actual operation (with dissipation and bellows pressure). And it does not depend much on how accurately the tongue and slot (entire reed) is made. However, it cannot give a complete description of the oscillations in air pressure (the acoustic sound) that the vibrating tongue produces. Let’s focus now on the acoustic sound, which is our prime interest.

 

In order to predict a complete description of the acoustic sound of the reed, we need to know how the vibrating tongue motion translates to oscillatory air motion, and this air motion needs to be understood in the near field (close to the vibrating tongue) and the far field (after the sound waves move to a region away from the reed – say to a region that is more than about ten tongue lengths away, which is the sound we hear). With a complete formulation, we will get some information on the acoustic near field, and here, we may be in luck, at least in so far as making conclusions about how different tongue materials might compare in their acoustic sound (volume and frequency spectrum, or timbre). These conclusions would be enabled because of the addition of a forcing function and dissipation terms into the E-B bar equation, and scrutinizing those terms. It’s the same way I suggested in my OP, only now we have more terms in the equation. The boundary conditions (B.C.) remain the same in this complete formulation (fixed at one end, free at the other).

 

In order to accurately determine what these terms are, we need to develop an accurate physical model for the tongue motion, and how this motion interacts with air movement. I developed such a model after I was invited to deliver a paper at the Acoustical Society of America 2017 meeting this last Dec 4 – 8 in New Orleans. I delivered the paper, with the published Abstract:

 

http://asa.scitation.org/doi/abs/10.1121/1.5014394

 

New Orleans was fun, and this paper is a work in progress. I have completed the physical model and have conjured a mathematical method of solution for the resulting governing equation and B.C. I now have to finish the formal solution - which at this point, is mostly a lot of Algebra - and to perform calculations and graphical results, check agreement with experiment, etc. But because of further travel plans out of the country, work on this project will be put off for more than a month.

 

I’m explaining all this in the hopes that I can convince a reed maker to first take up the simplest suggestion in my OP. By Spring, I should have completed the analysis and could hopefully make some statements about what geometry would be required to cajole two tongues of different material to not only vibrate with the same frequency and have the same overtones, but also to produce the same acoustic sound, if possible. It may not be possible. And of course, it may not be possible to find such simplistic generalizations from only this study, in which case, we would have to rely on an acoustical analysis of the air sound field. But let’s not yet give up hope on the simplest approaches first.

 

I wasn’t sure how to present all this, and I hope I haven’t confused things with my attempted explanation here. I’m glad to answer any questions, if I can. In the coming days, I plan to respond to the comments by others in this thread.

 

Best regards,

Tom

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Hi Johann,

 

Let's take the examples of steel and brass. Here's the suggestion:

 

[E/Rho]B x (aB)2 = [E/Rho]S x (aS)2

 

aB = [ (E/Rho)S / (E/Rho)B ]1/2 x aS

 

aB = (2)1/2 x aS

 

aB = 1.4 x aS

 

Thus, make the brass tongue thickness 1.4 times that of the steel tongue, and the tongue lengths, L, the same for both materials. This should guarantee that the modal frequencies of vibration will be the same for both tongues. And again, this should not depend upon how well the complete reed assembly is made. Concerning acoustic sound (timbre), we will have to investigate further into what geometries can be used to impart the same timbre, if possible. But let's go step by step.

 

Notice that the above result probably means that the brass tongue will be stiffer to the feel than will be the steel tongue, or in other words, the spring constant is higher for the brass tongue. This must be because the brass tongue, with higher density, will also be more massive than the steel tongue. The stiffness increases as the fourth power of the thickness (really the moment of inertia), whereas the mass increases only linearly with the thickness. Thus the effect of stiffness overcomes the effect of mass increase very quickly. The higher stiffness for the heavier tongue is needed in order to keep the mode frequencies the same for the two tongues.

 

Best regards,

Tom

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The other thought which comes to mind is the spring steel hardness which Wheatstone used to temper down to blue, but there was never any colours on Jeffries reeds which were very hard to file perhaps not tempered at all.

Al

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Hi Chris,
I suppose we have the usual interaction between a theoretician and an experimentalist. A theoretician might propose an experiment, but the experimentalist sees many practical issues that complicate the issue. This has occurred a lot in acoustics, and as an example, I’m sure you know of the attempts to decide the question whether vibrations in the body of a flute affect its acoustics. A suggestion for experimental insight is to build a metal flute and a wooden flute and see if the sounds are the same, and if they are, since the metal vibrations would be different than the wood vibrations, it suggests that body vibrations are not too important. The experimental difficulty of course is to build both metal and wood flutes to the same dimensions, which is not easy to do. But this is a digression.

 

So while the test would need to be simple in order to get done can I suggest the clearance between tongue and frame would need to be consistent across both examples?

 

 

I would say yes, when we are interested in timbre. As I mention above, it's probably not as critical if we were only interested in duplicating pitch, but this is basically a guess on my part.

 

does banging it with a hammer to work harden it only create a zone of surface hardness? What happens when you file it to create a profile, does it lose its hardness on the top? All of the brass I have here is "free machining", ie. includes a small percentage of lead. Can this be used? Does anyone have a working comparative knowledge of steel and brass profiles? Would brass and steel deliver the same pitch for the same physical profile and length and width dimensions? So many questions...

 

 

Since the entire mass of the brass will flow, banging it with a hammer will work harden the material throughout, and filing it will not reduce the bulk hardness. “Free machining” brass should work, and I think most any type of brass would work. Most all brass types come in three tempers: annealed (after heating and slow cooling), half hard, and full hard. Keep in mind that hardness does not affect Young's Modulus, but does affect ultimate strength. For the same length, a steel tongue should have the same pitch as a brass tongue that is 1.41 times thicker (as I calculated above). For a profiled tongue, the profiles in the different materials should be the same, percent wise.
If we are talking about using brass on its own merits, as opposed to an investigation into the reasons why different tongue materials sound differently, there are other practical considerations, and we touched on these in discussions on this news group years ago. I refer to two such threads:
Why Does Brass Sound Different Than Steel?
Why do Brass Tongues Break?
In the first of these, we discuss why brass tongues may sound different than steel tongues, bringing up the idea of tongue velocity and its effect on higher acoustic overtones.
In the second of these, we point out the concept of endurance limit for cycling stress in metals and reason that maximum stresses in brass need to be reduced because of its relatively low tolerance for repeated stress. One way to reduce stresses is to reduce the length of the tongue.
With both these discussions we see good reasons why brass tongues should play at lower volume, as David Elliot has pointed out in this thread, compared to steel tongues. I haven’t yet digested again all the posts in these extensive threads, but will probably find it necessary to do so as this investigation proceeds.
Hopefully, the complete solution of the fluid dynamical model of the vibrating free reed - as I’m pursuing according to the method I explained above - will provide the answers to most of the questions we have been asking.

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Tom,

Thanks for the gentle history lesson, I followed the links back to the previous conversations, which I had forgotten, and I can see I owe you an apology for throwing un-thought out and unattributed contributions into the current topic. Going back reading those discussions was to return to an old country with fewer shadows and one in which I seem to be a better thinker! A lot has happened since then.

 

Let me talk as one who in a lab might be called a reed technician. If your intention is to throw light on whether brass reeds sound different to steel ones then I am happy in this instance to do the technical work for you, up to a point, which is to say, if it is not too time consuming. Making a steel reeded assembly is not at all time consuming, one with a brass reed is a little time consuming, mainly in the developing of new skills. So that I can do. I will still have technical clarification questions; the two areas which come to mind have already been touched upon, clearances and brass hardening.

Sadly, there are two things I cannot understand. One is the concepts you express as equations. In another lifetime perhaps. The other is the technical terms you use ie. " Mathematically, it is called a non-dissipative (frictionless), homogeneous formulation, and the utility of it is that it (along with its boundary conditions) provides the eigenfunctions for any type of bar vibration consistent with its underlying simplifications..." and etc for the rest of the paragraph. I have no doubt I could get there eventually on that sentence but I have not the will nor the time.

So in order for us to get to what you want I will need you to be very prescriptive in simple terms. The aim, the projected method, how it will be tested. So far I have the initial aim as, to test whether the two sample reeds, steel and brass, will vibrate the same way. The method is; to make two reed assemblies, one with a steel reed, the other with brass, both with the same bar profile, width and length. The brass one to be 1.41 as thick as the steel. Evaluation methods yet to be discussed. Later we will look at timbre.

How am I going?

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Hi Chris,

 

Excellent!

 

I always hold out that some other academic type might join these discussions, and indeed, I would celebrate it. In fact, I know (of) a few, and I might drop them a suggestion. I have already invited Jim Cottingham, though I haven't gotten feedback on it, and I fully accept that they might not have too much interest. Anyway, that's the reason I sometimes stick in what I think are relative details suited for us academic types.

 

Best regards,

Tom

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