Enthalpy

PTFE too, and other weak polymers, are candidates for strengthening and stiffening. Making supermaterials is one goal, improving bad ones is one other. Creeping, flowing, low modulus all hinder the use of PTFE despite its other properties are good. Fibres exist already, hardened plates and rods would be nice. ========== "Schrägwalzen" is "skew rolling" in English, while "transverse rolling" includes other interesting possibilities. Common at tube production, it serves for rods too. Marc Schaefer, aka Enthalpy

More of the bass clarinet's nice sound, by Sebastian Tozzola: QwJo0tf1_7M - 8WbOXWgLeHg - mKGSmTWcfN8 - NjEu6Dd1Q9k - A4IQzeDcuDg

Still no oboe at hand, but Nederveen reports dimensions of two oboes (without chambers) on page 105 (pdf 113/118) of his PhD thesis Acoustical aspects of woodwind instruments so here's an update to the chambers of Jan 28, 2018. The tone holes are wider than I had imagined. When present, their chambers can usefully suppress the highest frequencies, say above 6kHz with banal dimensions. Suppressing down to 5kHz, or 4.5kHz, perhaps 4kHz, would better be done by additional Helmholtz resonators independent of the tone holes. Narrow inductors keep reasonable capacitor volumes. The highest suppressed frequencies can use quarter wave resonators if desired. The added resonators act also when the tone holes are open. There can be many resonators per octave of suppressed band. They can sit at the respective pressure antinodes. The resonators add lumped volumes to the air column, just like tone holes do. The known parry makes the bore a bit narrower and shorter in this region. The musician must access the narrow holes to dry and clean them. This applies to the oboe family, and easily to the bassoon family. Saxophones and tárogatók and candidates too, possibly with a special bocal or mouthpiece. ========== In the TutChamb archive here, the compiled cpp makes an exe which, fed with data from Make.txt, produces the renamed TutChamb.wav. From the artificial oboe's low B, "chambers" attenuate all components above a corner frequency, chosen here to attenuate two harmonics more per approximately 500Hz step. The programmed physical model isn't correct, but it attenuates. TutChamb_A.7z From the used initial spectrum, 20dB attenuation are useful but 40dB make no difference. In the 7 sounds, attenuation begins nowhere, then at 6kHz, 5kHz, 4.5kHz, 4kHz, 3.5kHz and 3kHz. 4.5kHz to 4kHz fits my taste. This is independent of the note height. Marc Schaefer, aka Enthalpy

Not very hot, but my guess is that the Vicat temperature is a first approximation. That is, hardened PE and PP would be usable at hot weather, little more.

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

Hello dear friends! Stretching stiffens polymers a lot, making wonder fibres of banal bulk materials. It brings LCP from 10GPa to 170GPa. Highly stretched polyethylene makes wonder ropes of Dyneema, Spectra and competitors. Stretching *3, easy with a polymer, strengthens much a stripe from a polyethylene shopping bag. Companies that stretch metal (for piano wire and others) could adapt to thicker polymer too. Or polymer manufacturers themselves could stretch or extrude the material cold or lukewarm, so mechanical engineers have stiff strong bulk polymers, lighter and easier to machine without fibre reinforcement. The transverse properties may drop. Rolling a polymer in two directions strengthens both, as polyester (Mylar) films show. This would improve plates. Sometimes the azimuthal stiffness too matters for rods. Schrägwalzen (I ignore the English word, check the drawings) de.wikipedia would improve the azimuthal direction, easy with a polymer. Combine with stretching or extrusion. Marc Schaefer, aka Enthalpy

Hello everyone! Copper tape is a thin copper band over adhesive tape, commonly used against electromagnetic interferences, seemingly also as a snail repellent. It used to cost a shiny penny for no reason, but the Chinese remedied that, check eBay and Alibaba. I should (I didn't try) be excellent to build antenna prototypes or indoor antennas, also outdoor antennas if protecting the conductors. Quickly assembled, modified, adjusted. Complete the contacts with the soldering iron. If the tape shall adhere on a flat item, then panel antennas, dipoles and dipole arrays, patch antennas, Uda-Yagi spring to mind. An optional second plane would constitute a reflector or director, and so on. A helical antenna fits on a cylinder, like a rolled PETP film. The supporting plane should have reasonable losses. PVC-PA no, wood-paper-cardboard if dry, walls no so good, PTFE excellent but poor adherence, PC-PMMA-PETP-ABS if thin, PE-PP-PS excellent, PS foam excellent, glass excellent including windows. The film's flat cross-section increases slightly the losses over a rod. Marc Schaefer, aka Enthalpy

I described the quasi-automatic system F for the oboe and similar here on Feb 09, 2020 updated Feb 23, 2020 scienceforums - scienceforums in a messages that contain much information at once. Maybe it helps if now I display only the notes played by finger 3L using its main and lone holes. Other fingers do the same, shifted uniformly by semitones. Following Obukhov, an X notehead tells that this one note is a semitone higher. Blue notes indicate 2L's main hole, orange, violet, green and yellow indicate lone holes. Figures tell on which mode (overtone) a hole emits the black played note. The main holes emit notes on modes 1, 2, 3, 4, 6 and potentially 8, 12, so each finger creates notes spaced by fifths, fourths and octaves. The oboe's conventional range ends on mode 2:3:4 (or 4 in short), but some scores demand more. The air column would reach much higher, my system too, the reed maybe. A tenor oboe has naturally a wider range than a soprano, a low saxophone too, especially if narrow like the tubax. This system F is a strong candidate for the soprito too scienceforums and subsequents The fifteen lone holes are evenly spaced by semitones. Their keys have one to three buttons each to combine with varied main holes so the different intervals favour different modes. The lone keys are sketched on Feb 23, 2020 too. Marc Schaefer, aka Enthalpy

I described the quasi-automatic system B for the basson family here on Jan 18, 2020 scienceforums in a message that contains much information at once. Maybe it helps if now I display only the notes played by finger 2L using its main and lone holes. Other fingers do the same, shifted uniformly by semitones. Following Obukhov, an X notehead tells that this one note is a semitone higher. Blue notes indicate 2L's main hole, orange, violet, green and yellow indicate lone holes. Figures tell on which mode (overtone) a hole emits the black played note. The main holes emit notes on modes 1, 2, 3, 4, 6 and potentially 8, 12, so each finger creates notes spaced by fifths, fourths and octaves. The Rite of the Spring's introduction fits on mode 3:4:6 (or 6 in short) and lower. The fifteen lone holes are evenly spaced by semitones. Their keys have one to three buttons each to combine with varied main holes so the different intervals favour different modes. The lone keys are sketched here on Jan 19, 2020 scienceforums Marc Schaefer, aka Enthalpy

The piano could play flageolet by adding limited hardware. It need a set of artificial "fingers" that touch the strings slightly at mid-length, or a 1/3 etc if this improves anything. Maybe of durable elastomer like PU or SI, or of hard material covered with felt. An additional pedal could move them simultaneously. Accuracy seems easier if each finger nears its strings spontaneously up to a stop and is lifted by a collective part. Addition to existing instruments looks feasible. I suppose the luthéal had the capability scienceforums The added expression is useful and of reasonable complexity, so we could generalize it. Marc Schaefer, aka 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.

As it looks, I botched that part. Diagrams of the input impedance versus the frequency are available on the Web for the trumpet and trombone, starting possibly with John Backus , The Acoustical Foundations of Music cited among others by hyperphysics.phy-astr.gsu.edu - newt.phys.unsw.edu.au The tuba must behave like the trumpet and trombone, with a first mode lower than half the second mode frequency and the pedal notes, not higher. So the useful "privileged tones" would result from some mode-locking between the sound's harmonics and the instrument's resonances, just as they are known to do with the pedal tones at the octave below. But then, why do the harmonics 3*M lock in modes 4*N for a tone a fifth below mode 2? The harmonics 2*M could also lock into 3*N for a tone a fourth below mode 2. Lower harmonics and a less low tone should favour that. Wiki's 39Hz is indeed an Eb, a fifth below the Bb second mode. On my tuba after 20 years, I'm not so sure.

Brass wind instrument have pedal notes. Bad and normally unused on the trumpet, not good on the tenor trombone, excellent and commonly used on the tuba and bass trombone, whose larger bore logically stabilize the lower modes. The first mode is not an octave below the second mode on my tuba. It's a fifth, nicely accurate. Wiki gives an exhilarating explanation for that: wikipedia It should be worth reminding that the "harmonic series" happens in cylindrical pipes open at both ends or closed at both ends, and nearly so in open conical pipes. The alphorn, cornetto, serpent, ophicleide are conical. The trumpet, flugelhorn, trombone, saxhorn, tuba, no usual brass is conical - just have a look at one. Modes 2 and over are aligned because the luthier adjusts the flare for it with much effort. The valves or slide need some cylindrical portion so the flare can't adjust the first mode to the octave. The "alternative resonance, false tone, or privileged tone" is the fully normal first resonance mode, just not at the height some people imagine. This resonance is fuzzy on a tuba but rather well tuned. I suspect the luthier carefully adjusts it to a useful and accessible height: the fifth combines nicely with the valves, and the harmonics 3, 6, 9... lock into modes 4, 8, 12... to stabilize the note and sound better. I didn't try if already the second mode of a baroque trumpet is out of tune, nor where the first mode is on a trombone, nor if a flugelhorn could imitate a tuba. Whether musicians impose with the lips a height that is not the first mode, and merely the harmonics locked in higher resonance modes give some stability? Marc Schaefer, aka Enthalpy

I proposed here on Mar 31, 2019 a construction with three slides and a compensator, but instead the semibaroque trumpet could have four semitone slides and no compensator. I see only advantages: The too low 7th mode isn't needed any more. The 4th mode joins chromatically the 3rd mode. The instrument is easier to play without a compensator. Trills get easier too. The construction with a fourth slide is acoustically as good as with a compensator. I kept a natural C instrument on the fingerings chart as precedently, and now the 3rd mode reaches a semitone lower than a modern Bb trumpet, but I feel wiser to shorten the tube to reach only the low end of the baroque repertoire and ease the highest notes. The general shape of Mar 31, 2019 remains, including mode holes with keys at the left hand. One loop shorter and one longer could look better and give more room to mode holes. The slide at 4R, which serves little for high notes, could be the last before the bell if this simplifies the mode holes. Marc Schaefer, aka Enthalpy

Hi everyone ! In shops, one remaining Covid contamination path is money. An answer is to allege that money doesn't host the virus, I read that. Or we can try to tackle the problem. UV light is known to destroy virusses, including Sars-Cov2. UV LED are available for near-ultraviolet Hg wavelengths, compact, reliable, efficient. This could irradiate the money between the cashier's and the customer's hands, in both directions. The rest is mechanical design, still imprecise. The apparatus must stop the UV from exiting but irradiate both sides of banknotes and coins. Both users could introduce the money at the top, say between a pair motorised soft rolls, and grasp it at the bottom, after an other pair of rolls. UV between the pairs of rolls would be blocked by the rolls. Nice for banknotes, but the coins would fall at once. It also needs a soft material that survives UV. This shape has the smallest footprint. Or a platter would tun slowly. The customer has a sector to introduce and extract money, the cashier has an other sector, and the two sectors in between irradiate the money under a cover. Silica and variants make the platter transparent to UV. Maybe banknotes and coins should have different paths. Possibly the soft rolls for banknotes and the platter for coins. The apparatus must be easy to open, and opening must halt the UV emission. Fluorescent surroundings would reveal any UV leak. Marc Schaefer, aka 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.

It may still seem exotic because unusual, as I proposed it only on July 28, 2019 here but a self-tuning harp will be that profitable: Imagine the sensors, motors and electronics sell for 42€ per string, totalling 2000€. A professional harpist who doesn't waste 2*15mn tuning a day saves his orchestra 400€/year. 5 years ROI. Over 6 years with that instrument, a harp student who saves 15mn tuning in 3h training becomes a paid professional 0.5 year earlier. Gain is 10* the cost.

Fewer people catch Covid-19 on Mondays. You can observe it on statistics for Germany, there n-tv.de Diagram titled "Fallzahlen-Trend Deutschland", click on "Differenz absolut", you get the number of new badly sick people per day. Mondays were 9, 16, 23, 30 of March 2020, 6, 13, 20, 27 of April 2020. This failed on 16 March, and the dip was a day early on 22 March. Tuesday 14 April dropped lower than Monday as it followed Easter Monday. Does this imply that people get contaminated on weekdays, but not on Saturdays and Sundays when staying at home? Not necessarily. The number of deaths too drops on Thursdays and Fridays despite the delay from contamination to possible death varies. See the diagram titled "Todesfälle in Deutschland". There must rather be some weekly fluctuation in the reporting tasks. Since Monday 27 April, more companies and shops are allowed to open in Germany. Some neighbour countries keeping strong mandatory isolation alledge that the number of cases increased consequently in Germany, but this is only the weekly fluctuation. Comparing with the week before, you observe a steady decline, nothing special since 27 April.

The contraforte has a wider bore than the contrabassoon, wider tone holes, and somewhat different fingerings. Compare on the same piece by the same professional musician, there: voices.washingtonpost.com The baritone oboe has a rather narrow bore jwu8WS5MAvA&t=325 the lupophone too but has wide tone holes -6gVdShhltg while the heckelphone has a wider bore Gxj0OLftfFk&t=30 - Gxj0OLftfFk&t=149 - Gxj0OLftfFk&t=274 - Gxj0OLftfFk&t=324 I wish to hear Katrin Stühle on a baritone oboe. I disagree that a wider bore gives a mellower sound. The sound is just - wider.

An other group plays jazz on bassoons: NNcmn5ovkJE Kudos to the arranger! And nicely played too.

Hello everybody! The contrabassoon is the usual contrabass in the woodwind section of a symphonic orchestra. Alas, it's not very loud, and most often a single one shall make the contrabass line for all woodwinds. The contrabass sarrusophone replaced it in the 19th century, mostly in France, but has disappeared. Other attempts were less known. And the excellent contrabass clarinet has a completely different sound. But presently, a loud alternative exists: the contraforte, by Guntram Wolf and Benedikt Eppelsheim guntramwolf.de and eppelsheim.com whose wider bore and wider tone holes give the expected louder sound. Fingerings differ, I ignore by how much. It can use a contrabassoon reed or a special one. The range is reportedly wide, but I trust the contrabassoon too for that. Here's a direct sound comparison. Lewis Lipnick plays both professionally and demonstrates Erwin Schulhoff's Bass Nightingale on both voices.washingtonpost.com More samples are available on Youtube (ymmv) and at Eppelsheim's linked page. The significant timbre difference is what you would expect. I feel replacing one by the other in a solo would need approval by the composer, but for the contrabass line among the woodwinds, you won't hear the timbre difference, and at least the contraforte is audible.

Wavefunction collapse, again. Changed my mind since 12/18/18. In an EPR experiment, the photon pair can't be emitted in all states. The argument is the same as against states decided at the emission: States with linear polarization would sometimes be observed by circular detectors, with no correlation between the detections. States with circular polarization would sometimes be observed by linear detectors, with no correlation between the detections. Even if all possible states, linear and circular, were emitted, the resulting correlation would be smaller than observed. In simpler cases where the states are exclusive, like the up and down magnetic moment for an electron, absorbed or not for a photon... a story like "both options coexist" is possible. Here with photon polarizations, we have linear combinations, and such stories don't work as is. I wonder how the parallel universes interpretation copes with that. EPR experiments are famous for supraluminal or simultaneous thingies, but there is worse. The particle that emitted two entangled photons was in a state that is decided when the photons reach the detectors, not before. Imagine a pair of transitions 3s -> 2p -> 1s: same momentum in 3s and 1s, the sum of the emitted photons' momenta is zero. But whether the photons were observed by a linear or a circular detector tells, back in time, that the 2p intermediate state of the electron too was linear or circular. This is possible because the intermediate state of the electron was not observed, so the backward propagation does not transport chosen information nor action. I had read vague allusions to backward "causality" in QM, it must relate with that. The conservation of momentum, angular momentum, energy... was already problematic with a reduction of the wavefunction, so backward propagation doesn't even need entangled photons.

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.

Hi everyone! Rocket nozzles must be short and light but make the flow as parallel as possible at the exit. Further demands exist in the atmosphere. The eggcup shape answers that but needs numerical optimisation. The thermodynamic state itself isn't algebraic, and a single point takes an effort to a PC. Dozens of chemical equilibria shift with T and P, notably 2CO + O2 <-> 2CO2. Condensation and solidification over the expansion, typically of Al2O3, worsen everything. The heat capacity depends heavily on the temperature. And limited heat exchanges between droplets and the gas would be useful to model. One common assumption is that the chemical composition shifts up to the throat but is frozen downstream as the expansion gets snappy. Even in the axisymmetric shape, combining the flow computation with the thermodynamic state in finite elements would be a very heavy computation. An improvement, supposedly banal, is to pre-compute a table of the speed modulus versus one variable like T, P or any convenient one, and use some interpolation. The computation load remains heavy. My proposal, and as usual I didn't check how common it is: Don't solve finite elements for the speed vector, as this demands to find simultaneously the thermodynamic state. Solve for the product of density and speed modulus. This conservation of mass is independent of the thermodynamic state. Its divergence is zero. It is even the gradient of a scalar harmonic potential if useful. When this product is known everywhere in the nozzle, the thermodynamic state can be injected from the inverted precomputed table that gives P, T, composition an so on as a function of the modulus of the product. Solving the finite elements gets easy for a PC. Solving for the product of speed and density applies also to other non-trivial flows, like the expansion of saturated steam. It's already useful for hypersonic flows of gases. ========== If any necessary, the 2D nozzle problem can become a 1D problem by adding a set of virtual flow sources (here tori) outside the nozzle walls and solving the intensity of the vitual sources that zeroes the flow through every wall section. One source behind each wall section, close enough for a decently conditioned matrix, far enough for even flow. The huge but hollow matrix of finite elements becomes a small but full one. If solving by iterations (less useful nowadays), the small matrix can be approximated by a band-diagonal one. A 3D problem also becomes a 2D one, with point sources behind area elements like triangles. The mass flow from each source is just R-2. The full matrix can be approximated by a multidiagonal one. This is "known" as I did it three decades ago, for a non-axisymmetric case, and other people may have done it before. Virtual flow sources apply where turbulence is unimportant and the virtual flow behind a wall doesn't matter, for instance at a turbine blade or a fast aircraft. Marc Schaefer, aka 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