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PostPosted: Wed Aug 22, 2018 6:11 am 
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Tunborough wrote:
Terry McGee wrote:
Forgive me if we've been here before (I am old enough to have a Papal Dispensation to pull this concession!), but tell (or remind!) me what the philosophic basis of your app is. Does it derive from Paul Dickens' work at UNSW, based on their acoustic impedance spectrometer, or drawn from some other source?

The Bibliography lists the sources for our modelling algorithms. The tonehole model, in particular, is the work of Antoine Lefebvre. For modelling the mouthpiece and the effect of the player, we took a somewhat different approach than Dickens. Rather than predicting a playing frequency directly, we predict the minimum and maximum frequencies at which a note will sound, on the assumption that these bounds are less dependent on the player (at least for whistles). "To predict the nominal playing frequency, the whistle model assumes that you will steadily increase the air velocity in the windway as you go from the lowest note on the instrument to the highest."


So, you are picking the points (above and below Fres) down the resonance peak above which a viable resonance can occur? So this would tell you max and min viable frequencies (the bandwidth?) of the resonance, and you can thus pick a mean frequency? And can thus derive Q value (Fres/BW?) which can intimate the vitality of the resonance? Or is that too simplistic?

Do you (can you?) look at the resonant frequencies of the upper partials? These might enable us to decide whether the bore diameter at this point, the hole diameters, the hole location or all of the above need tweaking.

I apologise for not checking this out in your site documentation. I'm just suffering from too-much-happening-in-my-life syndrome right now. All good stuff as it happens, but sheesh ....


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PostPosted: Wed Aug 22, 2018 6:11 am 
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Tunborough wrote:
Terry McGee wrote:
Forgive me if we've been here before (I am old enough to have a Papal Dispensation to pull this concession!), but tell (or remind!) me what the philosophic basis of your app is. Does it derive from Paul Dickens' work at UNSW, based on their acoustic impedance spectrometer, or drawn from some other source?

The Bibliography lists the sources for our modelling algorithms. The tonehole model, in particular, is the work of Antoine Lefebvre. For modelling the mouthpiece and the effect of the player, we took a somewhat different approach than Dickens. Rather than predicting a playing frequency directly, we predict the minimum and maximum frequencies at which a note will sound, on the assumption that these bounds are less dependent on the player (at least for whistles). "To predict the nominal playing frequency, the whistle model assumes that you will steadily increase the air velocity in the windway as you go from the lowest note on the instrument to the highest."


So, you are picking the points (above and below Fres) down the resonance peak above which a viable resonance can occur? So this would tell you max and min viable frequencies (the bandwidth?) of the resonance, and you can thus pick a mean frequency? And can thus derive Q value (Fres/BW?) which can intimate the vitality of the resonance? Or is that too simplistic?

Do you (can you?) look at the resonant frequencies of the upper partials? These might enable us to decide whether the bore diameter at this point, the hole diameters, the hole location or all of the above need tweaking.

I apologise for not checking this out in your site documentation. I'm just suffering from too-much-happening-in-my-life syndrome right now. All good stuff as it happens, but sheesh ....


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PostPosted: Wed Aug 22, 2018 9:01 am 
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Terry McGee wrote:
Now it would seem reasonable to guess that a wedge wouldn't present an aerodynamic problem in a whistle. As the whistle is endblown rather than sideblown (allegedly for our protection), there won't be any rotation of the vibrating air column.
Mostly, no problem, but if the base of the wedge is very thick, say half the height of the fipple block, the constriction in the bore under the window does mess with the tone.


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PostPosted: Wed Aug 22, 2018 9:27 am 
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Terry McGee wrote:
Tunborough wrote:
The Bibliography lists the sources for our modelling algorithms. The tonehole model, in particular, is the work of Antoine Lefebvre. For modelling the mouthpiece and the effect of the player, we took a somewhat different approach than Dickens. Rather than predicting a playing frequency directly, we predict the minimum and maximum frequencies at which a note will sound, on the assumption that these bounds are less dependent on the player (at least for whistles). "To predict the nominal playing frequency, the whistle model assumes that you will steadily increase the air velocity in the windway as you go from the lowest note on the instrument to the highest."


So, you are picking the points (above and below Fres) down the resonance peak above which a viable resonance can occur? So this would tell you max and min viable frequencies (the bandwidth?) of the resonance, and you can thus pick a mean frequency? And can thus derive Q value (Fres/BW?) which can intimate the vitality of the resonance? Or is that too simplistic?
The whistle model gets Fmax from the reactance of the whole system, and Fmin from the loop gain of the whole system--when the loop gain drops below 1, the whistle can't sustain oscillation in that register. With suitable breath control, you can play a note anywhere between Fmin and Fmax. Fmin-Fmax is a playing range, no relationship to resonance bandwidth. We have a model of pitch vs. air velocity between Fmin and Fmax, and make the following assumptions:

- You'll want to play the lowest note close to Fmax.
- You'll want to play the highest note closer to Fmin than Fmax.
- For notes in between, you'll want a regular increase in air velocity from note to note up the scale.

We draw a smooth curve from lowest note to highest note and use that to predict where the pitch of each note will land in normal playing. The Tuning Graph illustrates this graphically.

Out of interest, we do make a calculation of Q factor at resonance, but that isn't used in the tuning calculations.

Terry McGee wrote:
Do you (can you?) look at the resonant frequencies of the upper partials? These might enable us to decide whether the bore diameter at this point, the hole diameters, the hole location or all of the above need tweaking.
I have tried looking at the frequencies of the second and third harmonics to see if they explained errors in the model's prediction of fundamental frequency. I didn't see any correlation between the partials and the prediction errors, so WIDesigner doesn't bother to calculate them right now.


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PostPosted: Wed Aug 22, 2018 6:02 pm 
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To Keith Sandra: I assume you mean comparative benefits?

To Geoffrey Ellis:
I wrote a comment in response to you, but it seems off topic so I'll post a new thread about it.
The idea I have in mind is a single piece conical student flute.

[Edit: I am removing the rest of my post after listening to the recordings of Ellis' flutes. I realize my assumptions were based on my past experiences of fully cylindrical flutes, and aren't an accurate comparison or assessment considering the performance of his tapered-head cylindricals. I'll need to rethink things.]


Last edited by BlueSalmon on Thu Aug 23, 2018 3:01 am, edited 1 time in total.

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PostPosted: Wed Aug 22, 2018 7:24 pm 
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BlueSalmon wrote:
To Geoffrey Ellis:
I wrote a comment in response to you, but it seems off topic so I'll post a new thread about it.
The idea I have in mind is a single piece conical student flute.


I've actually done one-piece conical bore flutes. There are some challenges that make it a less attractive proposition from a manufacturing perspective, which is why I ended up doing the tapered head versions. Not very easy to swab out the bore on a one-piece conical bore flute either, being that it has to be done from the distal end which has about a 1/2" opening. Unless of course, they have a moveable stopper which can be taken out. That would oblige the player to use a very long stick to insert in the distal end and push the stopper out the top end. Again, it's doable, but not ideal. It would at least allow the bore to be swabbed out.

So the challenges can certainly be overcome. I made an F flute with a concial bore that turned out beautifully. A bigger pain than doing the tapered head versions, but the results were splendid.

And my other reason for the tapered head flute was that I'm trying to appeal to a broader audience than strictly ITM players. In ITM, the conical bore is the standard and it's what everyone seems to prefer given the choice. But there are a lot of Boehm flute players out there for whom the tapered head version feels very familiar and pleasing, and if they have a bent toward a folk instrument it might fit the bill. And of course lots of players who enjoy bamboo flutes and are looking for something a bit more stable with improved intonation, etc..

So I ended up trying to find something that would land in a nice, middle-ground where it would serve the needs of various types of players. And as Blayne demonstrated in those nice sound samples, an ITM player can certainly take these things to a session and get the job done.

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PostPosted: Thu Aug 23, 2018 1:20 am 
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Thanks Geoffrey for the thoughtful response and prompting me to listen to those clips. I'm sorry I didn't do so before posting. I had read your post, but must have skimmed past the last couple lines, as I tried to take in the whole thread quickly.

They're cylindrical? I would never have guessed that if I hadn't known. Amazing, congratulations on this, wow!
What performances too by the way, I'm glad to have heard these lovely recordings.

Re producing conical single piece flutes:
I guess I shouldn't be surprised that you've already tried this. I thought if anyone could do it, that it would be you, as I understand you have the mother of all flute drilling equipment.
I think the swabbing issue could be overcome, but I understand that production simplicity was one of your goals, to keep the flute affordable.
I've been thinking about moulding a composite conical flute, from natural fibers and binders. But as of now it's a pipe dream.


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PostPosted: Thu Aug 23, 2018 12:56 pm 
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I may have missed this suggestion before but is 3D printing a possibility.


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PostPosted: Thu Aug 23, 2018 1:38 pm 
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Normski wrote:
I may have missed this suggestion before but is 3D printing a possibility.

I would not be surprised to find that it's possible. As always, I think the biggest objection that players have to 3D printing is that they don't want a plastic flute. Obviously Delrin is a plastic as well (albeit a very dense one), and it gets a mixed reception.

I know that Geoffrey Guo (of Guo flutes) spent a lot of time, research, money etc. developing a line of injection molded Boehm flutes. I believe he has had an uphill struggle getting them to be accepted, simply because they are plastic. A friend who is a skilled player had tried one and he said they were pretty good for a plastic flute, but he didn't think they stood up well against comparably priced metal flutes, and (more importantly) he also didn't like them simply because they were plastic.

It's an interesting phenomena that people tend to have a natural affinity for more "organic" substances, or at least non-synthetic substances, and an aversion to synthetics. I don't know that it's rational, and it's certainly not universal, but it's a thing. When I went to the World Flute Society convention in 2016 with my headjoints, I had planned to take a bunch made from Delrin. It had made for some very nice headjoints, but my collaborator talked me out of it. He said the players wouldn't even look at it, and he was right. I surveyed a few and we showed a prototype to some others, and regardless of it's performance characteristics they were not interested. They just didn't want plastic.

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PostPosted: Thu Aug 23, 2018 1:44 pm 
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Interesting that, while there may be an affinity for "organic" materials, metals are accepted.

Maybe only organic metals.

Best wishes.

Steve

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"[Some flutists] place the flute between the upper lip and the nose, blowing the instrument from below. This position does not prevent good playing, but it does not look graceful."
~ Antoine Mahaut, 1759 in a tutor for playing the transverse flute ~


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PostPosted: Thu Aug 23, 2018 2:03 pm 
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Steve Bliven wrote:
Interesting that, while there may be an affinity for "organic" materials, metals are accepted.

Maybe only organic metals.

Best wishes.

Steve


Yes, I had the same thought! I suppose metal is perceived differently. I sort of get that. Metal is a natural substance that is refined and worked. Sort of like alchemy. I feel the same way about ebonite. It's made from natural ingredients and heat is used to transform it. In both cases, there is a "natural" quality to them that one doesn't experience with plastics.

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PostPosted: Fri Aug 24, 2018 8:13 am 
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Tunborough wrote:
Terry McGee wrote:
Now it would seem reasonable to guess that a wedge wouldn't present an aerodynamic problem in a whistle. As the whistle is endblown rather than sideblown (allegedly for our protection), there won't be any rotation of the vibrating air column.
Mostly, no problem, but if the base of the wedge is very thick, say half the height of the fipple block, the constriction in the bore under the window does mess with the tone.


I tried reaming a tapered head on one of my xiao (Chinese endblown flute with cylindrical bore) and had the same issue. I thought it would improve the intonation. In reality, the intonation on these flutes is already really good, so any improvement would have been small. But I found that it felt constricted and weakened the tone. So any small benefit it might have imparted was totally canceled out by this constriction.

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PostPosted: Fri Aug 31, 2018 6:01 am 
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Geoffrey

So it forces us to consider why the xiao has reasonable-to-good intonation whereas a plain cylindrical "Irish flute" is perfectly ghastly.

Am I right in thinking that xiaos (if that's a legitimate plural of xiao!) have absolutely zero "stopper" cavity. The embouchure is co-located with the node forming the stopper? So there is no "stopper cavity". That would be a major point of difference to our side-blown (allegedly for our protection) flutes?

Secondly, how big are xiao finger holes? Bigger than Irish flute? The bigger the holes, I imagine the less is the flattening effect in the second (and subsequent octaves). And therefore the less is our need to taper bore or head to compensate. (But that statement may need close examination.)

Are there other points of difference you can perceive? Let's get that far and regroup....


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PostPosted: Fri Aug 31, 2018 7:02 am 
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Terry McGee wrote:
Geoffrey

So it forces us to consider why the xiao has reasonable-to-good intonation whereas a plain cylindrical "Irish flute" is perfectly ghastly.

Am I right in thinking that xiaos (if that's a legitimate plural of xiao!) have absolutely zero "stopper" cavity. The embouchure is co-located with the node forming the stopper? So there is no "stopper cavity". That would be a major point of difference to our side-blown (allegedly for our protection) flutes?

Secondly, how big are xiao finger holes? Bigger than Irish flute? The bigger the holes, I imagine the less is the flattening effect in the second (and subsequent octaves). And therefore the less is our need to taper bore or head to compensate. (But that statement may need close examination.)

Are there other points of difference you can perceive? Let's get that far and regroup....


I have a few theories (or rather observations) about this. In an earlier post I commented on the surprisingly good intonation on the Indian bansuri, which I credit to a combination of hole size, wall thickness and stopper placement. Thin walls, large holes and (very importantly) a stopper that is moved quite close to the embouchure. When I make a bansuri in D, it varies from the more common cylindrical "Irish" flute in that it has a larger bore for the key (typically in the 21-22mm range) and the stopper is backset just a couple of millimeters from the near edge of the embouchure hole. On a narrower bore flute this seems to strangle the tone, but on the larger bore bansuri it works just fine, and the second octave intonation is impressive.

The xiao is a different animal. A xiao in D has a 17.3mm bore (.68") and small finger holes. The holes are uniformly sized on the outside of the bore, though I undercut most of them to varying degrees. Because it is endblown, there is no backset at all. In fact, because it is a notched flute, the "node" (on bamboo flutes) closes the end of the flute at the mouthpiece except for a small window under the notch. With open-ended xiao, the player's chin does the same, like on a shakuhachi flute. So this closed end is the virtual equivalent of having the stopper positioned half-way through the embouchure hole on a transverse flute! So right off the bat, that is going to help a lot with the flattening of the second octave. I believe this is the primary reason that the xiao has such good intonation. And I'm speaking specifically of the bei xiao, which is the version from Northern China (long and narrow with a capped end). There is another type from Southern China that is more like a shakuhachi, often made from root end bamboo that has a natural taper toward the foot, but that is another matter.

So effective is this design that with some pretty conservative undercutting the flute will play in excellent tune up into the third octave. It is very similar in some respects to the conical bore flutes we are all familiar with in that to get a nice tuning balance there are a couple of little compromises. The C natural note is very important in Chinese music, so to get it in good tune on the xiao, the maker has to tune the B note a hair sharp and the C# note a bit flat so that the cross-fingered C natural plays on target. But the intonation on a well-made xiao is as good as on any conical bore flute I've played. The xiao also has a lot of extra length in the body with six tone holes (two tuning holes and four vent holes below them). A friend who makes a study of this calls it the "tone hole matrix" and it has an effect on the harmonic character of the flute and the stability of certain notes. The physics behind it is out of my reach, but the Chinese makers figured this out centuries ago and made it part of the design. It is one of the coolest folk flutes ever. You can play ITM tunes on it if you choose :-) And because it is an 8-hole flute it has much greater range and versatility than a keyless Irish flute.

And because the design is so fully realized, my own modest attempts to "improve" it were hopeless. I tried a variety of experiments, from altering the notch size, to changing the tone hole matrix, altering the wall thickness radically and creating a taper at the head of the flute. In each case it was a backward step. I realized that hundreds of years of development went into this flute with a lot of clever makers experimenting with it, and it was a bit arrogant for me to think I was going to think of something they hadn't already considered. I don't think the flute can be improved, only changed so that it no longer sounds and behaves like a xiao. The tapered head brought no advantage and only strangled the tone.

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