Bore roughness and tone

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Re: Bore roughness and tone

Post by Nanohedron »

Terry McGee wrote: Mon Jul 05, 2021 7:24 amPerhaps those who feel they can perceive vibrations in their instruments can chime in here with their observations? Do any of the above possible explanations attract you?
I always perceived the phenomenon as being the body of the flute vibrating, which I simply - if unscientifically - chalked up to a perfect storm of harmonic frequencies making the structure vibrate (my dining room rings at F, for example); it's been years, so I can't immediately confirm, but I don't think I'd have that perception if my thumbs didn't sense the vibration too. Suffice it to say that it never felt like air to me. But this is all subjective, of course. Nevertheless it would feel as if the flute were alive and could jump out of my hands!
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Re: Bore roughness and tone

Post by BKWeid »

I once referred to this sensation as, "backpressure" in a C&F thread. The sensation that the flute is vibrating as if it were completely filled with air and resisting your effort. The sensation that the flute itself is vibrating and feedback is received through the hands, airway, and lips. My use of the descriptor, "Backpressure" was met with puzzlement and questions. I think we all experience that sensation when we are playing a particular flute well. I'm not sure how to describe it and it seems were not sure of the physics, exactly. To me, it is akin to the state of flow--everything clicking just right within your mind and body during an effort/skill, without much conscious thought. I wander off into the weeds...
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Re: Bore roughness and tone

Post by Nanohedron »

BKWeid wrote: Wed Jul 07, 2021 3:30 pm I once referred to this sensation as, "backpressure" in a C&F thread. The sensation that the flute is vibrating as if it were completely filled with air and resisting your effort. ... My use of the descriptor, "Backpressure" was met with puzzlement and questions.
I have distant memories of that discussion, or others like it (jeez, I sound like an Ent). I think "backpressure" is a decent and descriptive way to liken the sensation when, in my experience, you've hit that sweet spot where you're putting out not very much air jet at all, yet you're getting a whole lotta bang for your buck. As such, it can feel as if you're up against backpressure - even though it really isn't that. It's just that the embouchure is at (or near) its most efficient, plus the jet is at (or near) its best range of direction. Once it starts feeling like "backpressure", then the magic happens.

I don't think there's anything wrong with using "backpressure" as a metaphor, but it's probably best to remember that it's only a pretty good way to describe the sensation, and nothing more. If I were teaching I'd probably use the term myself (if figuratively), because it can give the student something conceptually concrete to hang their hat on. For me it works better than "fill the flute", which is another oft-heard way to describe it, although I admit the flute feels "filled".

There's also the sense of backpressure in the core bodily aspect of blowing into the flute, but that's about diaphragm control, and a completely different, if parallel and contributory, matter.
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Re: Bore roughness and tone

Post by skap »

Arthur Benade writes in his Fundamentals of Musical Acoustics:

"[...] At a subtler level, many kinds of things can lead to questions concerning the influence of materials:
when identical woodwind air columns are made using wall materials of different porosity or rigidity,
the resulting sounding pitch of the instrument may vary by as much as twenty cents; thin-walled
instruments on which one can feel vibrations are often improved (but sometimes spoiled) by putting
layers of adhesive tape on the outer surface at an empirically chosen spot [...]

Theory also poses questions, some of which are not hard to answer. For instance, it has been known for
many decades that the walls of a perfectly round pipe cannot vibrate enough to radiate audible sounds into
the room. When such a pipe is slightly out-of-round (elliptical), it can be excited much more strongly by
internal pressure variations, but even so it cannot radiate sound into the room with sufficient amplitude to
be heard in the presence of the other sources of excitation. Because of this, changes in the material or the
thickness of the walls cannot detectably alter the sound of an instrument insofar as it depends on radiation
by the walls.

The vibration of wind-instrument walls can sometimes influence the playing behavior significantly for
a different reason. Just as vibrations of the piano soundboard can alter the natural frequencies of the string
modes, so also wall vibrations can alter the frequencies of the air column. The air column “looks”
oversize at points of large wall vibration if the natural frequency of the wall lies above that of the air
mode which drives it, and undersize when this frequency relationship is reversed. I have seen instruments
(thin-walled metal flutes in particular) whose behavior seems perfectly insane unless the complex
influence of wall vibrations on regimes of oscillation throughout the scale is suitably damped out."
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Re: Bore roughness and tone

Post by Terry McGee »

Benade is a strange case, I reckon. His book is titled "Fundamentals of Musical Acoustics", yet he laces it with what I would call "exceptions and complications". E.G. "I have seen instruments (thin-walled metal flutes in particular) whose behavior seems perfectly insane unless the complex influence of wall vibrations on regimes of oscillation throughout the scale is suitably damped out." I haven't, and have difficulty even imagining such a circumstance. Perhaps I've lived a sheltered life!

But whatever, we can be confident that we are not in that surreal headspace. (Yes, treat that as a challenge!) Our great lumps of oddly-shaped hollowed-out tree do not pose much promise of any coherent mechanical resonance. (Don't believe me? Hold your flute at around the 2/5ths point and flick it in the middle with your forefinger held and then released by your thumb. Does it ring like a nicely-tuned marimba bar? Nah. It goes "thud".)

Ah, but even as I write, I am reminded of something I said earlier: "I'm not convinced we can feel vibrations in the bodies of our heavy-timber flutes, but I haven't tried to prove or disprove it. (Broad hint to next generation!). My feeling it's more likely that we are directly sensing the vibrating air column through direct contact via the finger holes. Having said that though, I did try one little experiment that might lead to the opposite conclusion. I took my Snark guitar tuner (set to vibration sensing mode, not microphone), clipped it onto a key on my keyed flute and played a scale. The tuner had no trouble following the action, which seems to suggest it was successfully sensing vibration. But was it vibration of the flute body or perhaps of the key reacting to the vibrating air column? One really needs to attach a vibration sensor with metering to various parts of the flute body itself before drawing too many conclusions."

Hmmm, this needs checking.

So I took the Snark (set to Vibration mode as I use it on the guitar), clamped it around the barrel of my flute, and played lower octave G. "G", Snark proclaimed confidently. Hmmm, how did the Snark know, I pondered. So I sang the note. Snark studiously ignored me. I switched Snark to Microphone mode and sang the note. "G", Snark agreed. Back to Vibration mode, sang G, ignored by Snark. In a rare moment of inspiration, detached Snark from flute and held nearby. Played G. Snark agreed wholeheartedly. Aha, there's your answer. Anywhere near the flute, the sound level is so high it excites enough resonance in the Snark body, or sensor, or both to register a reading. Indeed, if I hold it right in front of my mouth and sing really loudly, I can even sing a note it recognises. ["You OK there, Dad?" echo the kids from the kitchen....]

So we're not detecting movement in the flute body. We're detecting the intense sound field around the flute. As Oscar Wilde observed: "Nothing exceeds like excess."
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Re: Bore roughness and tone

Post by david_h »

I don't think I can feel vibration other than onto my fingers through the holes.

That Benade stuff reads like something Wikipedia would cover with warnings.
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Re: Bore roughness and tone

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david_h wrote: Tue Jul 13, 2021 6:31 amThat Benade stuff reads like something Wikipedia would cover with warnings.
That's not a fair linkage. Wikipedia forbids original research in its articles, whereas original research is what Benade does.
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Re: Bore roughness and tone

Post by Terry McGee »

The Wikipedia policy makes sense, Tunborough. Wikipedia needs thoroughly tested information if it's not going to end up looking flakey when Team B resoundingly refutes the work Team A just published.

I'd be interested to hear from you which of the woodwind acoustics writers you feel good about. Or if you think, for example, that modelling has supplanted theorising in our field? Where are we at?

People often exclaim "It's not rocket science." In two of my fields, flutes and bell acoustics, I'd agree. It's considerably trickier!
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Re: Bore roughness and tone

Post by an seanduine »

Terry McGee wrote: Thu Jul 22, 2021 12:21 am The Wikipedia policy makes sense, Tunborough. Wikipedia needs thoroughly tested information if it's not going to end up looking flakey when Team B resoundingly refutes the work Team A just published.

I'd be interested to hear from you which of the woodwind acoustics writers you feel good about. Or if you think, for example, that modelling has supplanted theorising in our field? Where are we at?

People often exclaim "It's not rocket science." In two of my fields, flutes and bell acoustics, I'd agree. It's considerably trickier!
Terry, I think you are right. . .I can readily understand how something as simple as the V-1´s pulse jet engine worked. . .but after a while Benade and Nederveen give me a headache. :poke:

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Re: Bore roughness and tone

Post by Terry McGee »

Ah yes, the V1, Hitler's flying bomb, or Doodlebug as they came to be known in England at the time (according to my late mother who worked at a Christian Brothers' academy in London during the war until they were decamped to the Lakes District to protect the children). The name came from the unusual sound of the rocket engine.

One interesting common factor between bells and flutes is the fact that the partials can be inharmonic (which is why we shouldn't call them harmonics!). And a bell with inharmonic partials can sound pretty awful. When they cast bells they are cast too thick and therefore too high in pitch. The bell tuner then mounts the bell upside down on a vertical lathe (looks more like a mill) and skims out the excess metal from various parts of the bell, being careful to keep an eye on each of the first 5 partials so that, when the job is over, each of the partials is within about 5 cents of ideal. It's a real dark art!

Inharmonic partials in flutes can also sound bad, but possibly worse, they can also sound weak. The efficiency of the jet-switch depends on all the partials lining up to give the jet a good coherent nudge. A good example of poor partial alignment is the very flat low D of early 19th century English flutes. Played "normally", the low D on such flutes is weak and a bit dismal sounding. Which is why Irish players learned to offset the jet to drive most of the energy into the upper partials (the "Hard D").

I'm always fascinated by the interaction over time between the instruments, the makers, the players and the music. Not just in our own music, but across the world, in every music. It's magic at work. "Hubble bubble, toil and trouble, fire burn and cauldron bubble...."
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Re: Bore roughness and tone

Post by Tunborough »

Terry McGee wrote: Thu Jul 22, 2021 12:21 amThe Wikipedia policy makes sense, Tunborough. Wikipedia needs thoroughly tested information if it's not going to end up looking flakey when Team B resoundingly refutes the work Team A just published.
No argument there. The intent of Wikipedia is entirely different than the Fundamentals of Musical Acoustics.
Terry McGee wrote: Thu Jul 22, 2021 12:21 amI'd be interested to hear from you which of the woodwind acoustics writers you feel good about. Or if you think, for example, that modelling has supplanted theorising in our field? Where are we at?
There's certainly no one I'm qualified to cast shade on. I've got Benade, and Fletcher and Rossing, at hand here. Over the last few years, I've seen some really interesting work coming out of the Lutheries - Acoustic - Music team of Benoit Fabre and colleagues.

I'm way behind in my reading, but I think modelling is still in its early stages. There remains a lot of work to be done in observation, measurement, and experimentation, from which to build theories and models.
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Re: Bore roughness and tone

Post by david_h »

Tunborough wrote: Wed Jul 21, 2021 8:24 am
david_h wrote: Tue Jul 13, 2021 6:31 amThat Benade stuff reads like something Wikipedia would cover with warnings.
That's not a fair linkage. Wikipedia forbids original research in its articles, whereas original research is what Benade does.
All the same, it is three paragraphs with no specific reference to original work substantiating the statements made. In particular "... it has been known for many decades that..." in academic writing is usually decoded as "I couldn't be bothered to find the original references" .
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Re: Bore roughness and tone

Post by pancelticpiper »

Terry McGee wrote: Tue Jun 15, 2021 5:07 am How could he (or anyone) tell what aspect of the roughened bore was original, and what was wear accumulated over the centuries?
Some of the originals were in pristine condition, appearing to be without wear of any sort.

Add to that, what sort of wear would make a bore rough?

The opposite, actually, as I discovered years ago. 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.
Terry McGee wrote: Tue Jun 15, 2021 5:07 am I would imagine that, even back in the baroque day, makers would have polished and sharpened their reamers to yield a pretty slick bore.
The Baroque flute maker in question didn't attempt to guess what the 18th century makers would have done, rather, he studied what they did do.

Personally I think that 150 years of Boehm flutes has got everyone accustomed to gleaming polished smooth bores.

BTW the same has happened in Highland pipemaking!

Around 1980 some Highland pipemakers began touting gleaming mirror-smooth polished bores.

Thing is, old Highland pipes aren't like that, even presentation sets which were never played, having been stored in museums since they were made.
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Re: Bore roughness and tone

Post by Terry McGee »

pancelticpiper wrote: Sat Jul 24, 2021 7:24 am Some of the originals were in pristine condition, appearing to be without wear of any sort.
So probably largely unplayed. It's been posited that old flutes found to be in pristine condition were probably not much fun to play. Possibly an extreme position, but certainly one worth considering. Perhaps a more generous reading would be that they were built late, and that changes going on at the time (eg from 1-key to 4-key etc) rendered their practical lifetimes short.
Add to that, what sort of wear would make a bore rough?
Just playing, but especially playing without mopping. Moisture from the breath raises the grain. Remember how fine furniture builders scrape their surfaces to a fine finish, then damp them down to raise the grain, before scraping them or sanding them again before applying the finish. If they didn't do that, applying the finish would raise the grain, producing a very disappointing outcome.
The opposite, actually, as I discovered years ago. 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.
Yep, I've come across flutes like this, including modern flutes. And when asked, the owner admits that they play it, then set it down without mopping it out. I'm sure that happened way back when as well.
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.
Again, I'm not surprised. Somewhere further up I commented on the nature of the fuzz that seems to grow when you wet a reamed bore. It looks awful, in terms of how non-reflective of light it is, but doesn't take that much work to polish away. And the measurements once polished are not significantly altered. It's a surface effect, unless perhaps taken to extremes over a very long period. So enough work with a dry cloth swab would get you there. And keep you there.
Terry McGee wrote: Tue Jun 15, 2021 5:07 am I would imagine that, even back in the baroque day, makers would have polished and sharpened their reamers to yield a pretty slick bore.
The Baroque flute maker in question didn't attempt to guess what the 18th century makers would have done, rather, he studied what they did do.
Must be great having a time machine to be able to go back and do that! Without the time machine, how can you be sure what's original and what's wear?
Personally I think that 150 years of Boehm flutes has got everyone accustomed to gleaming polished smooth bores.
Hard to know. Remember again that the cabinet makers of the era were accustomed to achieving very fine finishes. And glancing up the bores of a number of old flutes I have here reveal gleaming bores. But against that, I have one old flute that had been found in shearer's quarters somewhere up the country, and it's bore is appalling!
BTW the same has happened in Highland pipemaking!

Around 1980 some Highland pipemakers began touting gleaming mirror-smooth polished bores.

Thing is, old Highland pipes aren't like that, even presentation sets which were never played, having been stored in museums since they were made.
I wonder if it makes much difference with Highland pipes, given the robustness of the driving reed (compared to our airy-fairy "air reed").

Does a significant amount of the moisture from the breath make it all the way to the chanter, or does it remain trapped in the bag? Putting the question another way, do Highland pipers feel the need to mop out after playing? Do they need to empty the bag?
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Re: Bore roughness and tone

Post by Conical bore »

Terry McGee wrote: Sun Jul 25, 2021 3:58 am
pancelticpiper wrote: Sat Jul 24, 2021 7:24 am Some of the originals were in pristine condition, appearing to be without wear of any sort.
So probably largely unplayed. It's been posited that old flutes found to be in pristine condition were probably not much fun to play. Possibly an extreme position, but certainly one worth considering. Perhaps a more generous reading would be that they were built late, and that changes going on at the time (eg from 1-key to 4-key etc) rendered their practical lifetimes short.
A third reason might be a non-professional musician, a wealthy banker or landowner who had a go at the flute or the pipes, found out it was harder than it looked, and retired it for display on the shelf as a nice decoration.

Sort of the equivalent of high-end custom electric guitars right now, which I've heard described as being marketed to "Blues Lawyers." Guys who can't really play, but like owning these guitars and can afford them. These guitars look pristine when they eventually come onto the used market because they've never been played.
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