Woodwind Materials

[Enthalpy]

13 hours ago, Enthalpy said:

Shall the luthiers contract a plastic injection company to make rods for subsequent machining?

Rods would be made by extrusion, not injection, so the unusual resin costs no new tool.

[Enthalpy]

Here on Nov 13, 2017 and Nov 26, 2017, I proposed the oval deformation of the wall around side holes to explain the material's influence.

Curving the air column would stiffen the wall as it gets a curvature in two direction then. It can be significant with metal walls since they're thin usually.

For instance a metal contrabass clarinet, a metal contrabassoon, a sarrusophone, a tubax... could be built with the air column curved all the way, like a Wagnertuba, some baritone saxhorns or a French horn are, rather than as straight sections connected by sharp turns. What makes little or no difference at brass instruments might improve woodwinds.

Shall the flute be curved, a bit like the serpent was? That won't ease the keyworks, but it would shorten the alto flute and hopefully stiffen its wall, which is too thin and of bad alloy because of the weight.

Marc Schaefer, aka Enthalpy

[Enthalpy]

A wind instrument with a mostly curved air column, as inspired by the Wagner tuba or the serpent for instance, is made easily by electroforming or by filament winding. Polymer injection would be conceivable for certain wall thicknesses.

Intended for woodwind, this could apply to brass instruments too if desired.

Marc Schaefer, aka Enthalpy

[Enthalpy]

Could liquid crystal polymer make mouthpieces for single-reed instruments like the clarinets, the saxophones, the tárogató?

Mouthpieces are widely made of ebonite up to now, sometimes of metal or "crystal" (a glass variant). LCP would keep ebonite's warm contact, resistance to saliva, mechanical damping, and multiply Young's modulus by 5, which might ease the emission of the altissimo register. Loading increases the modulus further, especially with graphite choppers. At least Vectra A950 is authorized for food contact by the FDA. LCP can be processed by injection to make cheaper mouthpieces.

Marc Schaefer, aka Enthalpy

[Enthalpy]

Instrument parts were already electroformed. Conn made its "Coprion" trumpet bells starting around 1938
cderksen.home.xs4all.nl link there to a Conn flyer
other sources are indirect: Bach and Schilke are said to electroform their silver bells, but I havent found the claim on Schilke's website. Here a manufacturer electroforms copper trumpet bells:
dqscustomshop.com

So at least it has worked, but the process didn't replace other methods.

• The electrodeposited metals are in perfectly annealed condition, and apparently the luthiers tried only pure copper and pure silver which are horribly soft then. Easily deposited nickel is harder even if pure, and nowadays alloys are deposited too, including Cu-Ni, Cu-Sn, Cu-Zn, Ni-Co and many more, while Ni-Mo, Co-Mo, Ni-Co-Mo and Ag-Cu, Ag-Pd, Ag-Rh look favourable.
• Electroforming boots, bocals and complete woodwind bodies with chimneys would save more time than trumpet bells.
• Electroformed keyworks would be lighter or stiffer or both, especially saxophone octave keys. This demands a hard metal.

Ag, Au, varnish... can cover allergenic Ni and Co.

[Enthalpy]

Here's one company that makes instruments with bells and necks of graphite fibre composites:
dacarbo.ch with jeccomposites.com
using graphite filaments plaited in situ and fabrics.

I believe filament winding would save human labour. Other polymers may be more durable and damp better than epoxies: polyketone, LCP?

[Enthalpy]

Wound filaments are commonly impregnated with a thermosetting resin. A molten thermoplastic would be nice, since polyketone, LCP, ABS, PP are vibration dampers and resist humidity better. Or could the resin be dissolved to impregnate the filament for winding? I could make a glue for  ABS by dissolving ABS chips in trichloroethylene or maybe acetone. Ketones supposedly dissolve polyketone and exist with any evaporation rate. A warm mandrel would evaporate the solvent faster there.

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As a variant of the idea of Dec 16, 2018 here, filament winding can make two bells at once.

This doubles the production for nearly the same human effort and reduces the scrap. The winding head also moves between nearly cylindrical ends, which should be simpler and enable a cheaper machine with fewer axes. Winding can provide thicker ends where the bells' inner face is ground.

Marc Schaefer, aka Enthalpy

[Enthalpy]

Body material for an alto flute is a difficult choice.

D=24mm often, so 0.38mm of 92.5% Ag, with E'=98GPa and rho=10370kg/m³, would bring the elliptic deformation resonance of a full cylinder to 1490Hz, within the alto's range. 0.43mm would reach 1690Hz, a mere semitone above the written C's fundamental, but the harmonics are much higher, and the body resonates lower at the tone holes. The heavier and longer body excludes thick metal for flutists except weightlifters.

Yamaha use rose brass for its alto and bass flutes. Interpreted as CuZn15, its E=122GPa E'=139GPa and rho=8750kg/m³ save 16% mass and raise the resonance by 1.30 at the same thickness. At least the elliptic resonance of a full cylinder is a bit above the fundamental range, as on the soprano flute. Though, most flutists prefer silver over copper alloys.

Dalbergia wood family seems too heavy. 4mm thick, the naked body would be longer and weigh 2.25* as much as a 3mm soprano, for which many flautists find wood heavy. Big Dalbergia pieces are also difficult to find and fragile. Graphite fibre composites thick enough to save chimneys, as for instance Matit does for soprano flutes, would be too heavy too.

==========

Graphite filament winding can bring high resonances and light weight. With isotropic E'=100GPa and rho=1550kg/m³, 2mm are lighter than brass and a plain cylinder resonates at 20kHz. It would require glued chimneys or subtle winding that lays more filaments around the holes.

Maybe a polymer loaded with graphite choppers can be decently machined despite being abrasive. Rods of POM-CF and damping ABS-CF are available, polyketone and LCP should outperform them. For ABS-CF, E'>18GPa and rho=1200kg/m³ let a 2mm plain cylinder resonate over 9.9kHz, while the brass mass would allow 3mm composite.

The outer profile would be milled after the bore is drilled. A bore centered in the rod just needs a 40mm rod. Extrusion (and reaming) seems possible. The tone holes would be drilled and profiled as in wood. I imagine metal plates glued on the body to hold the keyworks.

Flexural modes with ABS-CF would be as fast as with rose brass. LCP-CF would improve a bit.

This can inspire other instruments like the clarinet, especially low ones.

==========

The other path is a curved body, as suggested here on Mar 22, 2019 on 12:44 AM and 01:23 PM.

Marc Schaefer, aka Enthalpy

Edited March 31, 2019 by Enthalpy

[Enthalpy]

Some wooden flutes have silver tenons to connect the joints, for instance Yamaha's YFL-874W and YFL-894W
europe.yamaha.com
which reduces the risk of cracking and saves the extra wood thickness to accommodate the overlap and the cork. Also, it introduces no deep lossy groove in the air column when tuning the flute down.

The manufacturer also claims "adds focus to the sound", "adds tonal body" and the ubiquitous "improved projection", the usual spiel.

Or could there be something in it? I proposed here on Oct 30, 2018 that the tone holes couple the air column's vibration with the body's bending modes. Lossy silver tenons dampen the bending resonances. They should act better than cork, which is too soft to dampen stiff wood efficiently. At these places, little silver would have a big effect, including for wood or polymer bodies.

If experiments confirm an effect, silver tenons should be generalized wherever they are robust enough. Or cobalt-nickel, copper-manganese and other lossy alloys. Not only at wood, also at polymer and graphite fibre bodies. Beyond flutes, also at oboes, clarinets, of course bassoons, pretty much all woodwinds, brass maybe too.

Marc Schaefer, aka Enthalpy

[Enthalpy]

Tone holes let a woodwind body vibrate as they break the symmetry, so are there vibrations at the mouthpiece of a single-reed instrument?

Let E=2.5GPa and rho=1400kg/m³ for ebonite. The dimensions are from a soprano clarinet.

==========

Where the bore meets the reed, the mouthpiece section is open hence more flexible, and the sides may vibrate laterally.

For hand computation, I model the U shape as a flat part hold at the middle, 4mm thick, 2*13mm wide. Per metre length, EI=13 and µ=5.6. The first flexural resonance, with k*13mm~pi/2, occurs around 3.6kHz.

The fundamental of a soprano clarinet doesn't reach this frequency. Amateurs are expected to reach written G an octave above treble clef, so the resonance would be the H₃ of a high note. For professionals who reach higher notes, it could also be H₂. Resonance would affect the emission of a note and its timbre, as we hear these frequencies well.

How much? Static 1Pa would deform the tips by 0.27nm, creating a displacement of 9*10^-15m³. For comparison, a D=14.6mm L=0.4m air column (*0.5, the mean value of cos²) contains 33cm³, which 1Pa compress by 2.4*10^-10m³, so the mouthpiece's lateral deformation is 26000* smaller.

Now, ebonite may resonate with Q=40, so the deformation is 650* smaller and its phase dissipative. Accounting ideal bore friction, conduction and radiation for a clarinet at 3.6kHz, but not the losses at the tone holes, Q~50, which the /650 deformation reduces to 46.

The effect is small. But if ebonite had been half as thick, the effect 8* worse and at a note's fundamental would have been annoying. Once again, existing designs are good but don't take huge margins.

Metal puts stronger resonances at higher frequencies, which should make no difference here. It's more a matter of accurate manufacturing, thermal comfort, condensation. Polyketone with E=1.3GPa would need a bit more thickness, while liquid crystal polymer with E=9GPa could accept less. Ease of manufacturing can decide.

==========

Pressure oscillations act vertically on the mouthpiece, stronger than at tone holes, and the opposite force on the reed acts only at the ligature, but the mouthpiece's tip vibrates little thanks to its stiffness.

I make a very coarse model with thickness constant over the length. The first resonance is then around 7kHz and the displaced volume 5* smaller than for the sides lateral vibrations. Nothing to worry about.

==========

The reed and mouthpiece end transmit strong vibrations downstream, possibly to the instrument's body. The big area at a pressure antinode has more potential than the closed tone holes effect described here on Nov 13 and 26, 2017.

If the musician didn't apply his teeth and lip, the opposite pressure forces on the mouthpiece and reed would compensate at the ligature, because the reed resonates at a frequency exceeding much the sound, so its inertia is negligible and the reed transmits all the force over the ligature.

The stiff teeth and skull reduce the mouthpiece's force, the softer lip at the reed's strong movement too. How much of each remains is impossible to evaluate from my armchair, sorry for that, but they won't compensate an other. The skilled musician reduces the reed's vibration amplitude with his lip consistency to obtain a mellow sound, so much of the force is absorbed.

The cork isolates strongly the barrel or bocal from the mouthpiece's vibrations. A tenon of absorbing material like silver would be stiffer and damp the resonances too.

Some mouthpieces have a softer insert for the teeth. It limits the transmission to the skull and internal ears, but may also damp the mouthpiece's movements. This, together with the mouthpiece's mass, could make a difference to the listener, more so at low instruments.

Marc Schaefer, aka Enthalpy

[Enthalpy]

Most woodwind have corks where the joints fit in an other, and corks let woodwind bodies vibrate lengthwise.

I take E=G=6MPa and losses=2.2% @1kHz for cork
amorimcorkcomposites.com
unexpected small losses, but cork does rebound, more so than many elastomers.

==========

Let's take a soprano clarinet as an example, with D=14.6mm bore taken as uniform. At the mouthpiece, 1Pa creates 0.17mN axial force. At the fittings, the oscillating air pressure acts on D_o~20mm D_i=14.6mm to create forces as strong. The bell's flare too experiences axial forces.

It the corks are 10mm long and 3mm thick (I have no clarinet at hand), their axial stiffness is 1.3MN/m. This resonates a 20g mouthpiece around 1.2kHz, and together with a 30g barrel at 0.8kHz. The bell resonates somewhat lower, and the driving force can originate elsewhere. If the upper and lower joints weigh 0.15kg each, their fitting resonates them around 0.6kHz. Or rather, these resonances combine. The joints, especially the bell, add their own lengthwise resonances.

The frequencies reside at the fundamental's lower clarion to the upper registers, and at the strongest harmonics of the chalumeau register. Bad luck.

1Pa and 0.17mN would move the parts by 0.13nm in quadrature, but Q=45 resonances amplify this to 6nm in-phase. Facings create a lossy pulsation of 10^-12m³.

Compare with the air column: 1/2* 0.25m D=14.6mm make 21cm³ where 1Pa induce 1.5*10^-10m³. A clarinet has Q>100 at these registers, so the lossy pulsation is 1.5*10^-12m³. Corks create much losses at a clarinet, according to this model - but experiments decide as usual.

It would be worse at an oboe or a bassoon, where the bore is a smaller fraction of the wood section.

Q=45 lets affect one note and the neighbour semitones for being so strong. The resonance is too wide to conceal it between two notes, cork is too variable too.

Not only is power lost. The blowing resistance is smaller, and the emission of the upper register may become harder.

==========

A century ago, woodwinds had impregnated thread coiled on the tenons and bocals. Did it resonate less strongly? I didn't compare when I let install corks at my bassoon, alas.

Many elastomers resonate less than cork does. Perfluoroelastomers are an extreme case, they are also hydrophobic and they glide well. Others are easier to glue and cheaper. A limit is that damping materials creep, so the fitting eases over time.

==========

Some wooden flutes have silver tenons to connect the joints, for instance Yamaha's YFL-874W and YFL-894W
europe.yamaha.com
I had suggested  that these tenons dampen the flexural resonances, here on
Apr 01, 2019
they look also excellent to dampen the lengthwise resonances at the fittings of all wind instruments, since silver absorbs vibrations and is also stiffer than cork: 150MN/m for D=14.6mm e=0.35mm L=10mm. I take a perfectly stiff contact between the metal rings.

On metal flutes, the bare accurate adjustment is airtight and slides gently, thanks to thin metal. I suppose that metal tenons in wooden flutes have a location where the diameter doesn't follow the deformations of wood. Maybe ebonite is stable enough that mouthpieces don't need an inner metal lining and the manufacturers don't learn new materials and fabrication methods. But the luthiers and workshops not used to flutes would have to learn adjusting metal rings.

Besides (sterling) silver, PCM is a good instrument alloy, and some Ni+Co alloys are known dampers that can be electroformed too: easier for pure oboe or bassoon luthiers. More here on
Nov 04, 2018

At a flute B-joint, the fitting is already much shorter than what a clarinet, oboe or bassoon needs. At a conical bore, the fitting must be cylindrical, hence a bit wider that the cone upwards and narrower downwards. Thin metal needs less wood thickness than cork and keeps more sturdy joints.

When a clarinettist tunes his instrument down, this creates presently cavities at the air column with deep corrugations. Metal fittings improve this. But the chamber of a saxophone has important functions, so a new design must keep it.

Marc Schaefer, aka Enthalpy

[Enthalpy]

According to Cary Karp, who studied two remaining oboe da caccia made by Eichentopf
jstor.org - wikipedia
the body was first machined straight, then (gashes) kerfs were sawed at the rear side, the remaining wood bent over steam, a slat glued at the rear, and voids filled. Playing copies were made in recent times the luthiers know the missing process steps.

My tiny contribution: let make a cutter to mill the gashes accurately. It can have precisely the needed shape, except for the rim that needs a minimum width. The conical shape demands cutting edges as far from the rim as the gashes are deep, and the cutter's radius can exceed this much. Several cutters on a shaft can work more quickly.

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I've already suggested to cut wedged body segments completely from an other and glue them together as a curve
scienceforums
and here's an illustration:

Slats can usefully hold the segments precisely in place while glueing, especially if they press against accurate flat surfaces made at the body before segmenting.

==========

Both processes apply to polymers too, including polyketones and liquid crystal polymers, except that heat rather than steam softens them. I had already suggested electrodeposition
Jan 01, 2018 - May 02, 2018
and filament winding
Nov 01, 2017
to produce curved body parts. The two present processes need a different know-how, possibly more accessible to pure woodwind luthiers.

Good glue joint aren't easy on polymers. Glueing POM is known. Solvents can prepare a surface for glueing or make the joint Few solvents are known for polyketones: hexafluoroisopropanol, meta-cresol, and the more benign solutions of ZnCl₂, ZnBr₂, ZnI₂, LiBr, LiI, LiSCN that leave residues. Solvents for liquid crystal polymers are uneasy too: pentafluorophenol, trifluoroacetic acid. Though, slats alone won't bring much stiffness not toughness.

Welding polymers is better than glueing them when possible.

Many woodwinds need or would benefit from curved body parts of wood or polymer: alto and lower clarinets, bassoon and contrabassoon, baritone oboe, alto and lower tárogatók.

Marc Schaefer, aka Enthalpy

[Enthalpy]

Following the message of Jan 15, 2018, here''s one more comparison between grenadilla and Pmma oboes, both from Marigaux and played by the same musician, in the same bad room full of echo:
rBEysvPiYPY at 0:34 and 1:38
and I hear exactly the same difference as with the other oboist: Pmma sounds like a piece of plastic, especially at the low notes. Simply the wrong material for a woodwind.

It's even surprising that the difference is so strong and repeatable. Possibly the oboe depends more on the walls materials than other woodwinds.

[Enthalpy]

The musician must slide fingers from one key to an other at many woodwinds, for instance the thumbs at the bassoon.

Coating the keys with nickel that embeds Ptfe powder should help. I let coat steel parts with it, and they were more slippery to the fingers. The good property lasts indefinitely.

Nickel provokes allergies to many people, so a different metal that can embed Ptfe would be better. It must resist corrosion.

Plain material also exists that embeds Ptfe powder, for instance sintered bronze to make plain bearings. It can't be cast nor brased at high temperature, but machined, filed and soldered at low temperature yes.

Marc Schaefer, aka Enthalpy

[Enthalpy]

Here's the flute head stopper I made around 1992 and have been using since.

It needs only to turn and bore one part. Mine happens to be Ptfe. The O-rings are banal, maybe Nbr.

The metal rod moves the stopper when inserted in the hole.

I noticed no difference with the usual stopper, but a decent flute might let perceive one.

Marc Schaefer, aka Enthalpy

[Enthalpy]

The air column of some woodwinds makes a U-turn: at the bassoon family, the low clarinets, past and maybe future low oboes...

The ones I saw are of metal that fits over corks at tenons at the wooden body (the saxophone differs). This must dampen the sound, like cover pads do, because the metal tube is light and the cork soft.

I suggest to fit the metal U-turn in the wooden or polymer body with a metal lining, like Yamaha do for their wooden flutes
scienceforums - scienceforums
europe.yamaha.com

The stiff contact between metals should improve more here than between straight heavy wooden flute joints. Very useful too, these fittings are short, so tone holes can have better locations.

The metal parts can be electroformed as already suggested
scienceforums and followers
They probably need adjustment, as for flutes and brass instruments.

Wood expands much with moisture and heat, flutes' Dalbergia less, bassoons' Acer more so, while metal expands little.

• Yamaha flutes cope with that.
• The metal lining could fit narrowly in the wood at one end and fit narrowly over the metal tenon at the other, possibly with some elastomer there. Or fit the wood at both ends and the tenon at midlength.
• Wooden joint have reinforcing hoops at their ends, of metal often, of graphite fibres on some clarinets. An adjusted amount of fibres would let the wood fit the metal's thermal expansion.
• Present bassoons have both bores in a single wooden part. A global hoop of graphite fibres would stabilize the bore spacing. Trumpets can cope with some spacing mismatch.
• If separate wooden parts make both bores, metal parts can assemble them. Pyramids would stiffen all directions
  scienceforums - scienceforums

Whether the bell of a bass clarinet can hold at such a fitting? I'd rather put the U-turn higher, and some toneholes on a rising wooden joint, especially for clarinets reaching a written C as they're uncomfortably long.

Marc Schaefer, aka Enthalpy

[Enthalpy]

Ahum. The boot of my French bassoon is completely different, and for the drawing of Jan 04, 2020 03:58 PM I looked at an old instrument that is NOT the usual U-bend of present bassoons.
Yamaha (Fox resembles much) and Heckel page 3/12

These constructions use very little air column length. Not an advantage of my proposal.

About the stiffness:

• The gasket, often cork, brings little stiffness.
• The screws are stiff but they hold at one end in wood whose shear isn't quite stiff.
• The other end holds on a metal plate whose bending stiffness decides.

Said plate looks thick. Depending on exact figures, which I won't infer from small pictures, the standard design may or not be already stiff enough.

As a small variation of the standard design, two elastomer O-rings could replace the cork gasket, especially if retained. Then, a shape that presses the metal tube directly against the wood at the bores, or rather against metal glued on the wood, would gain stiffness if needed.

Electroforming would make the intricate shape at once, as already said, but the plate shall not be too thin.

Marc Schaefer, aka Enthalpy

[Enthalpy]

I had thought cork grease and keyworks oil would benefit from elaborate synthetic alkanes, but just vegetable oils seem excellent, and wouldn't evaporate over decades. As simple as palm oil as a grease, palm kernel oil as a light oil, maybe treated a bit more
https://www.chemicalforums.com/index.php?topic=56069.msg360960#msg360960
For sure, they're cheaper than cork grease selling for 5€/15g.

[Enthalpy]

I've bought 1kg of palm oil for 1.5€ and while I wouldn't put that in my stomach, as a cork grease it's fabulous for music instruments. Tallow must have been that good.

Zero odour, vegan, no known allergies, should fit many faiths. Share the 150¢ among 60 musicians if you wish. Or repackage in 15g units and sell each for 5€.

Few reasons exist to improve over that, with chemical treatments or from a different start. The indicated shelf life is one year, so time will tell if it smells. The added canola oil leaves a hard grease that takes longer to rub, no drawback for me. Playing only indoors, I can't tell the sensitivity to temperature.

Marc Schaefer

[Enthalpy]

I suggested liquid crystal polymer (LCP) for wind instrumens body and more parts. Graphite choppers increase E=11GPa to E=23GPa, exceeding Dalbergia melanoxylon. But cutting tools may wear out faster.

LCP is known to stiffen quickly and strongly along the injection direction. Often undesired in injected parts, this effect gives LCP fibres E=270GPa, and would improve a body made from extruded or injected raw material. Instruments accept a transverse stiffness somewhat lower, so adjustment room is available.

Stretched LCP could then be stiffer and denser than Dalbergia melanoxylon but spare the cutting tools.

Marc Schaefer, aka Enthalpy

[Enthalpy]

I explained that the tone holes of a woodwind can excite the body's bending modes, here on
Oct 28, 2018 and Oct 30, 2018
because pressure pushes everywhere, but the force at the finger or cover mainly accelerates it, and is little transmitted to the body, hence the net side force.

A flute blowhole too results in a net side force that can excite the body's bending modes. Here the pressure accelerates air at the blowhole, and much like in a rocket engine, this force doesn't balance the push at the opposite wall, creating a net thrust. But how much?

I take an already estimated 1411Hz bending mode of a soprano flute, well within its fundamental mode, and evaluate the force for 1Pa at the pressure antinode as previously.

• The speed at a pressure node is 2.4mm/s in the D=19mm tube
• At a rounded 13mm*10mm blowhole, air is faster: 5.5mm/s and 49m/s²
• The blowhole is 6mm high, but end effects add 6mm to the inductance. 12mm air take 0.7Pa to accelerate, nearly 1Pa.
• Consistent: 12mm height of narrow blowhole are as inductive as 28mm cylinder length, and lambda/2pi=39mm.
• 0.7Pa push 13mm*10mm air by 86µN while 1Pa push D=13.5mm cover by 143µN. That's 0.6* as much as on one cover.

This contribution is significant. More toneholes can contribute to shake the body, but if they spread over several flexural half-waves, their effects cancel out partly. Also, a flute fundamental exceeds 2100Hz, the harmonics more, and air inertia at the blowhole increases the pressure drop.

This net push under the blowhole excites also the already described elliptical deformation at the headjoint. That would justify the head's material, beside the damping of the global flexural modes. It would also explain why Dalbergia melanoxylon outperforms silver at piccolo headjoints.

A velocimeter would tell how important the effect is.

At least against elliptic deformation, the parry is to add material, preferably damping one, around the tube in the blowhole region.

Marc Schaefer, aka Enthalpy

[Enthalpy]

To estimate the effect of walls on a wind instrument sound, I checked up to now the frequency response of the air column in the walls. This might implicitly let suppose that the sound spectrum results from a resonator filtering an independant generator. But this is not the case.

The reed, blowhole or lips are fully coupled with the air column to make the oscillator. Here, the resonator uses to influence the sound more than if it only filtered the fixed spectrum of an independant generator.

For reasoning, let's imagine that the negative conductance is linear. The oscillator sounds on every resonator mode whose conductance (loss) leaves a negative sum. Resonator modes whose conductance is too big are not excited at all.

Though, the negative conductance can't behave linearly. Even if the resonator attenuates much a component, the reed, blowhole or lips can recreate some, so the situation is complicated. It's even inaccessible to algebra generally, so I won't go beyond the previous qualitative explanation.

[Enthalpy]

I suggested here on Jun 02, 2019 that corks leave elasticity between body joints and let them vibrate.

A compagny called Lefreque sells "sound bridges" that are applied across both joints to transmit the vibrations
lefreque.com

Usual question: does this change anything? Here's not a trial report but physicist's thoughts.

• A cork fitting is a good target, see my linked message.
• Is a pressure contact stiffer than a wide long thin cork? For accelerometers at audible frequencies, we prefer thin glue over screw pressure.
• A brass mouthpiece fitting in a metal cone is much stiffer than the "sound bridge". What would improve? Dampen side vibrations?
• Replacing cork with metal, especially silver, would bring hugely more than adding a "sound bridge". Done on Yamaha wooden flutes. See my linked message.
• The website promises the usual spiel. This doesn't imply all is wrong. A company won't explain a true invention. And the "sound bridge" may improve a clarinet but not a trombone.
• The "spectral analysis" shows notes at different frequencies, not partials better aligned. Hopefully the "sound bridge" does not shift the frequency by shown 1% as this would ruin the instrument.

[Enthalpy]

Voichita Bucur published her
Handbook of Materials for Wind Musical Instruments
apparently in September 2019 as a file and coming in July 2020 on paper.

A chapter targets:
Effect of Wall Material on Vibration Modes of Wind Instruments
link.springer.com
Some diagrams can be seen over Google Images by searching
"Vibration modes of wind instruments"

The transfer functions show some influence by the walls, depending on their damping, whose direction, magnitude and frequency range is compatible with the two first models I proposed: elliptical deformation and body bending.

[Enthalpy]

As wall material for woodwinds, stiff E=18GPa wood like Dalbergia melanoxylon is preferred over more bendable species, while musicians disdain polymers with E=3GPa or 1GPa.

Stretching stiffens polymers a lot, making wonder fibres of banal bulk materials. I already proposed it for bodies of LCP
scienceforums
and stretching would stiffen polyethylene, polypropylene and others too, without fibre reinforcement hence keeping the good machinability.

Polypropylene makes already bassoon bodies at Fox-Renard, insensitive to moisture without any liner, but with a lacklustre sound that wall resonances may explain
scienceforums - scienceforums - scienceforums and following

Highly stretched polyethylene makes wonder ropes of Dyneema, Spectra and competitors: E~100GPa is expected in this category.

Stretching *3 strengthens much a polyethylene stripe from a shopping bag, easy with a polymer. The process is accessible to luthiers. Companies that stretch metal (for piano wire) could also adapt to thicker polymer.

Or polymer manufacturers themselves could harden the material, if enough mechanical engineers want it
scienceforums

Possibly the transverse properties drop, but thick walls have margins at woodwinds. If the azimuthal direction matters, the polymer manufacturers could harden it too.

Marc Schaefer, aka Enthalpy