Bore roughness and tone

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Re: Bore roughness and tone

Post by Terry McGee »

Yeah, good point, Conical. And I guess it was always thus. Maybe it's a cunning Marxist plot? We flute makers would starve to death if dependent on the slim earnings from the relatively small number of professional musicians out there. So make flute playing fashionable, and the big end of town will support it!

Any "Flute Lawyers" out there, feel free to contact me at.....
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Re: Bore roughness and tone

Post by skap »

What is relevant for this discussion is that 18th century originals have rough bores today (whatever the real reason is),
and their tone is described (today) as soft. Now, what is a soft tone ? Officially it means less higher harmonics,
more fundamental, right ? I think, however, that the attack is very important for how the tone is perceived (and
in psychoacoustics they consider it as a constituent of the perceived timbre, it seems). I've discovered that my two "identical"
GA Rottenburgh's have identical spectrum when the note is sustained, but the attack time is significantly different.
The smoother, more gradual attack of the wooden instrument makes for a tone that feels softer, warmer, with more depth.
The delrin instrument gives a sound that appears rather suddenly, is more tricky to "shape", and feels tiresome in the
long run for my ears. Obviously, all the articulation feels different and should be "fine-tuned" for each one (the wooden
instrument feeling more natural articulation-wise, eventually).

Now, I have no idea how people define the flute's response. For me, it was rather the stability with which a note can be
produced and also the lowest volume at which the sound can still be maintained without turning into a hiss. But not the attack
time. But this discussion makes me think that people link the response to the attack time.

Now if it's the attack time that is influenced by the roughness/smoothness of the bore, and not the spectrum of a sustained note,
that seems much more plausible. At this transitional phase the air flow may still be very important, and doing some reading
I've learned about the acoustic streaming in woodwinds, a quite interesting phenomenon.
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Re: Bore roughness and tone

Post by Conical bore »

skap wrote: Mon Jul 26, 2021 6:16 am What is relevant for this discussion is that 18th century originals have rough bores today (whatever the real reason is),
and their tone is described (today) as soft. Now, what is a soft tone ? Officially it means less higher harmonics,
more fundamental, right ? I think, however, that the attack is very important for how the tone is perceived (and
in psychoacoustics they consider it as a constituent of the perceived timbre, it seems).
The note attack on a flute would seem to me to be very difficult to pin down with relation to bore smoothness affecting the attack for better or worse. It's not a very "attacky" instrument compared to many others, and there are so many different ways to begin a note. There is tonguing in various degrees of hardness, glottal stops, taps and slurs where it's just the fingers opening and closing the bore holes that create a note attack. All very different in sound, and each one of us will do it a bit differently.

I suppose it would be possible to test this with a mechanical gadget of some kind that interrupts an artificial airstream across the embouchure hole. You'd have a baseline for "attack" and could compare different bore roughness to see how that affected tone. The results might not be relevant for every player though, since some of us play with "hard" attacks (tonguing and glottal stops) while others use a more legato, finger-based phrasing.
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Re: Bore roughness and tone

Post by skap »

Conical bore wrote: Mon Jul 26, 2021 8:17 am
skap wrote: Mon Jul 26, 2021 6:16 am What is relevant for this discussion is that 18th century originals have rough bores today (whatever the real reason is),
and their tone is described (today) as soft. Now, what is a soft tone ? Officially it means less higher harmonics,
more fundamental, right ? I think, however, that the attack is very important for how the tone is perceived (and
in psychoacoustics they consider it as a constituent of the perceived timbre, it seems).
The note attack on a flute would seem to me to be very difficult to pin down with relation to bore smoothness affecting the attack for better or worse. It's not a very "attacky" instrument compared to many others, and there are so many different ways to begin a note. There is tonguing in various degrees of hardness, glottal stops, taps and slurs where it's just the fingers opening and closing the bore holes that create a note attack. All very different in sound, and each one of us will do it a bit differently.

I suppose it would be possible to test this with a mechanical gadget of some kind that interrupts an artificial airstream across the embouchure hole. You'd have a baseline for "attack" and could compare different bore roughness to see how that affected tone. The results might not be relevant for every player though, since some of us play with "hard" attacks (tonguing and glottal stops) while others use a more legato, finger-based phrasing.
I'm talking about the inherent attack time of the flute which will be of course amplified by the tonguing technique. I feel like I have to
really restrain my articulation on the delrin flute to get the desired nuance. I'm into baroque music so different shades of tonguing are needed. A wooden flute seems much more enjoyable in this context. For my experiment I started a note in the exact same way (by simply lowering the air jet without any tonguing) on the two flutes while recording. Visualized the frequency spectrum when the note is settled in, and superposed the two plots: almost identical, like fingerprints, all harmonics match, didn't even expect that. Yet sounds different, even in the recording (wooden flute sounds softer). Clipped the beginning of the notes and listened again: indistinguishable.

I've heard before that in psychoacoustics experiments people even have hard time identifying completely different instruments when the attack is clipped. But despite the diversity of attack techniques used by different players in different musical contexts you always recognize the instrument, so there is something inherent to the instrument. It may be more than just the attack time, in fact, but maybe different harmonics rise at different rates (I don't seem to be able to analyze this).

Until reading this discussion and then delving into some literature, I was sure it was the vibrational properties of the material (in the
sense of Benade describing it: interaction between the air column vibration with inner wall vibration through resonance). But the evidence against this theory is appalling (including my little experiment). Further, the two flutes are from the same maker, I don't see why he would "voice" them (if it's even possible) so drastically different. By the way, now that I know what to listen to, I notice the
same "nervousness" of the attack in my injection molded Aulos Stanesby Junior (and I have at present two other Stanesbies: one in blackwood, one in ebony, to compare with). And it seems to be valid for recorders as well. This special thing that the wood brings
is maybe the character of the attack and not the harmonics distribution of the sustained note. And if it's not the vibrational properties of the material, it must be the smoothness of the bore, or where would this difference come from?
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Re: Bore roughness and tone

Post by Loren »

And if it's not the vibrational properties of the material, it must be the smoothness of the bore, or where would this difference come from?
Occam’s razor, eh?

IME flute acoustics, including your specific example, are more of a Hickam’s dictum affair.
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Re: Bore roughness and tone

Post by an seanduine »

Occam of course was a Platonist by my reckoning, Hickam appears not.
Is there an Ideal Flute?
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Re: Bore roughness and tone

Post by david_h »

skap wrote: Mon Jul 26, 2021 10:36 am Further, the two flutes are from the same maker, I don't see why he would "voice" them (if it's even possible) so drastically different.
Maybe customers for the different materials tend to be looking for something different. See the drift of many discussions here.

I can almost always tell the difference in sound between a metal and wooden boehm flute. But I suspect it's mainly because the people I hear who play wooden boehm's are looking for - and playing so as to achieve - a different sound to the ones who play metal boehm's. They may have chosen a flute that helps them get it and the maker made it to help that. If they were to play a metal flute would I notice the difference, even if *they* did?

For me that's the simplest reason for the difference. There may be others.
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Re: Bore roughness and tone

Post by skap »

david_h wrote: Mon Jul 26, 2021 1:33 pm
skap wrote: Mon Jul 26, 2021 10:36 am Further, the two flutes are from the same maker, I don't see why he would "voice" them (if it's even possible) so drastically different.
Maybe customers for the different materials tend to be looking for something different. See the drift of many discussions here.

I can almost always tell the difference in sound between a metal and wooden boehm flute. But I suspect it's mainly because the people I hear who play wooden boehm's are looking for - and playing so as to achieve - a different sound to the ones who play metal boehm's. They may have chosen a flute that helps them get it and the maker made it to help that. If they were to play a metal flute would I notice the difference, even if *they* did?

For me that's the simplest reason for the difference. There may be others.
As far as I know, customers who buy baroque flutes (or recorders) in synthetic material, are looking for an instrument as close to a wooden one as possible. If the maker was to make some special adjustment for this material it would certainly be in the direction of making it sound as a wooden one, not the opposite.
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Re: Bore roughness and tone

Post by skap »

Loren wrote: Mon Jul 26, 2021 11:15 am
And if it's not the vibrational properties of the material, it must be the smoothness of the bore, or where would this difference come from?
Occam’s razor, eh?

IME flute acoustics, including your specific example, are more of a Hickam’s dictum affair.
Well, the nature itself seems to favor Occam's razor. All the physical laws are stunningly simple.
Wherever there is complexity and confusion, it just means we are still far from the truth, or maybe
we are not asking the right questions.
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Re: Bore roughness and tone

Post by Terry McGee »

Skap, you've mentioned your two otherwise-identical Rottenburghs, one in wood, one in poly. Is it possible with these to swap the heads over? Do the characteristics seem to follow the heads, or be shared between the two mixed flutes?

One area we have to be very careful of is the sharpness of the embouchure edge. Poly is capable of taking a very sharp edge, wood less so. I feel the very sharp edge can make the flute feel "twitchy" or "scritchy".

You also mention:
I've heard before that in psychoacoustics experiments people even have hard time identifying completely different instruments when the attack is clipped. But despite the diversity of attack techniques used by different players in different musical contexts you always recognize the instrument, so there is something inherent to the instrument. It may be more than just the attack time, in fact, but maybe different harmonics rise at different rates (I don't seem to be able to analyze this).

You could try Waveanal, a program written by Bill Hibberts for the analysis of bell sound. The various partials in bells tend to swell and decay at very different rates, hence Bill's interest in providing a means for measuring this. It should work for flute notes as well - Bill assures me it's based on straightforward FFT analysis techniques, and should therefore have relevance beyond bells. (Just ignore any assignment of the peculiar partial names we use in the bell world!) It's a bit klutzy - you need to upload the audio file with the note you want to analyse, then look for the Find Decay button in the Partials section at bottom right of screen. Then save the decay data as a spreadsheet file, and then open it in a spreadsheet and graph it.

Waveanal and its documentation can be freely downloaded from Bill's website: http://www.hibberts.co.uk/
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Re: Bore roughness and tone

Post by Sedi »

Terry McGee wrote: Tue Jul 27, 2021 4:13 am Poly is capable of taking a very sharp edge, wood less so. I feel the very sharp edge can make the flute feel "twitchy" or "scritchy".
Some or rather most of the embouchure cuts I made are so sharp, you could probably cut something with it. I used aluminium or plexiglass for the lip plate. I noticed no twitchiness - it's easy and stable to play. In fact, I think it comes closer to a "woody" sound than the delrin flute I own.
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Re: Bore roughness and tone

Post by skap »

Terry McGee wrote: Tue Jul 27, 2021 4:13 am Skap, you've mentioned your two otherwise-identical Rottenburghs, one in wood, one in poly. Is it possible with these to swap the heads over? Do the characteristics seem to follow the heads, or be shared between the two mixed flutes?

One area we have to be very careful of is the sharpness of the embouchure edge. Poly is capable of taking a very sharp edge, wood less so. I feel the very sharp edge can make the flute feel "twitchy" or "scritchy".
Thanks, Terry. Great idea. Not that I haven't thought about it before, but didn't want to mess with the threads as the two headjoints didn't seem to be readily interchangeable. Finally, only minimal adjustments were needed. The characteristics do seem to follow the heads and not the bodies, so you must be right about the embouchure cut. I also tried to experiment with some whisper tones. It is as if the delrin head was too eager to develop a fuller sound, I don't know if it corresponds to what you describe as "twitchy" or "scritchy". Will certainly pursue these experiments, as in such subtle matters hasty conclusions may be wrong.

I've made a totally unrelated discovery in this experiment. The delrin Rottenburgh has a very difficult 3rd octave F, basically unusable without half-closing the 5th hole, while the bubinga Rottenburgh's high F is pretty good with the standard fingering. I've discovered that the high F totally follows the body and not the head.

Thanks for the link to Waveanal, that looks really interesting, I will certainly try to find time to try to learn how to use it. For now, I tried to analyze the spectrum of some whisper tones and it seems that bubinga's whisper tone contains 5 harmonics while the delrin's whisper tone has a tendency to only have the first 3 (at that moment I already swapped back the bodies, so will have to repeat it with the headjoints next time). That's only one note though, and it's quite possible that my whisper tones were not very consistent.
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Re: Bore roughness and tone

Post by Loren »

skap wrote: Tue Jul 27, 2021 3:06 am
Loren wrote: Mon Jul 26, 2021 11:15 am
And if it's not the vibrational properties of the material, it must be the smoothness of the bore, or where would this difference come from?
Occam’s razor, eh?

IME flute acoustics, including your specific example, are more of a Hickam’s dictum affair.
Well, the nature itself seems to favor Occam's razor. All the physical laws are stunningly simple.
Wherever there is complexity and confusion, it just means we are still far from the truth, or maybe we are not asking the right questions.
The laws of aerodynamics, for example, may be “simple” but that doesn’t mean designing the aerodynamic body parts for an F1 car is a simple task due to the interplay of multiple surfaces involved. A little change in one place causes changes elsewhere.

Flutes are the same. You are attempting to ascribe one perceived aspect of performance to a single instrument part/finish. However If one makes a bunch of woodwinds and pays attention, one realizes that it doesn’t quite work that way.
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Re: Bore roughness and tone

Post by Terry McGee »

skap wrote: Tue Jul 27, 2021 9:21 am Thanks, Terry. Great idea. Not that I haven't thought about it before, but didn't want to mess with the threads as the two headjoints didn't seem to be readily interchangeable. Finally, only minimal adjustments were needed. The characteristics do seem to follow the heads and not the bodies, so you must be right about the embouchure cut. I also tried to experiment with some whisper tones. It is as if the delrin head was too eager to develop a fuller sound, I don't know if it corresponds to what you describe as "twitchy" or "scritchy". Will certainly pursue these experiments, as in such subtle matters hasty conclusions may be wrong.
Good, skap. That seems consistent with our general experience, that overall performance is usually a head thing (unless pulled down by a dramatic issue in the upper body).

One think I've come across in delrin is that it prefers to flow rather than be cut. This can lead to a "wire (or wicked) edge" at places like the embouchure. Google the term if not familiar. I think dealing with the "wire edge" is important.

Image
I've made a totally unrelated discovery in this experiment. The delrin Rottenburgh has a very difficult 3rd octave F, basically unusable without half-closing the 5th hole, while the bubinga Rottenburgh's high F is pretty good with the standard fingering. I've discovered that the high F totally follows the body and not the head.
Yep, again consistent with experience. (Comforting!) Interesting to see if you can work out why! Contenders could be variations in the bore tapering, sizes of holes, undercutting or lack thereof, etc. The third octave is a scarey place in flutes, and all the more so in small hole flutes like baroque instruments. Here a tiny change can have big implications!
Thanks for the link to Waveanal, that looks really interesting, I will certainly try to find time to try to learn how to use it. For now, I tried to analyze the spectrum of some whisper tones and it seems that bubinga's whisper tone contains 5 harmonics while the delrin's whisper tone has a tendency to only have the first 3 (at that moment I already swapped back the bodies, so will have to repeat it with the headjoints next time). That's only one note though, and it's quite possible that my whisper tones were not very consistent.
Heh heh, again consistent with experience. These flutes would be so much more reliable if not blown by humans!

It's possible that Waveanal might balk at the shorter partial rise times we expect from flutes compared to bells, but worth a look. There may be other fields that have developed useful analytical approaches we should look at.
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Re: Bore roughness and tone

Post by Terry McGee »

Coming back to something pancelticpiper mentioned earlier:
I bought a c1860 London-made flute in overall good condition, however the bore was rough all along the very bottom, all the way from the top of the body section to the bottom of the foot. It looked like the flute had been stored horizontally with water from playing left sitting in the bore.

I played this flute for around 30 years, always swabbing it after I played. The regular swabbing gently polished the bore, eventually smoothing out the roughness of the bottom.


Today I was about to polish the bore of a flute I was working on that I had purposefully previously "raised the grain" on. So looking down the bore it was dark and gloomy, clearly rough to eye and finger. Sounds like pancelticpiper's flute except the grain was roughened all around, not just along the bottom. And I thought, let's try out the idea of swabbing, to see what would happen.

I used a piece of fairly rough cotton rag, large enough that it would only just pass through the head section, when attached to a typical flute cleaning rod. Figuring that when we swab a head, we push the rod in and then pull it back out, I defined a single to-and-fro motion as 1 swabbing. I did 50 swabbings, then reviewed the results.

It was interesting. The bore looked much brighter now, reflecting light entering the far end, but you could still make out a faint screw pattern with about a 1.5mm pitch (1/16"). I wondered if it related to the speed at which I had progressed the reamer through the head - that as the head rotated one turn in the lathe, I pushed the reamer in another 1.5mm. Given the length of a head about 160mm, that would involve the head rotating just over 100 times as I advanced the reamer. Seems plausible.

So 50 swabbings with a dry cotton cloth had polished most of the finer raised grain, but not the underlying reamer marks, whereas, when I polish the raised grain with fine abrasive paper and finish with fine steel wool, there are no visible blemishes remaining. And after the 50 swabbings, the bore still felt a bit rough to the finger. So it's not just a visual effect.

This seems to suggest that the old makers probably did polish their bores after reaming, as I don't remember seeing much in the way of reamer marks. Although perhaps that many swabbings would erase even them!

So, if you have a flute with a dull or slightly roughened grain, some serious swabbing might be enough to sort that out. But if its really roughened or even corrugated (as I've seen some), abrasive papers and steel wool will save you a lot of time.

But remember, whatever you do, you are also removing the protection of oilings past. So re-oil the flute and let it dry before pumping more moisture through it!
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