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Łukasz Martynowicz

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Everything posted by Łukasz Martynowicz

  1. I must agree with Ruediger on this one. But before I will add my two cents, I want to be clear - I definately appreciate your concertina playing here, what I have to say is about emotional content of the arrangement itself (and this is of course purely personal opinion). Hurt is one of my favourite NIN songs and the original Johny Cash version is playing right now as I'm writing this post (I didn't knew that NIN rendition was a cover). And I must say, that I haven't ever even focused on lyrics before (I'm not a native english speaker and I focus mostly on musical content when listening to songs in foreign languages) but still, both NIN and Cash versions have VERY strong choruses, and in both cases the overall construction of the melody tells a very strong emotional story with the music layer itself (NIN IMHO even stronger than Cash). For me, it could even be in Suahili or Chineese and it would make the exactly same emotional impact. Your version has no such effect - it makes me completely indifferent to the meaning of the lyrics. One reason for this is that you have dropped a very significant, steady beat in the chorus that builds up the tension and instead you slow down at the begining of the chorus, loosing the grip you have build up on the listener. And the second reason is that your vocals are very smooth and ornamental - very "polite" compared to strong and harsh "cry" in Cash and NIN versions. But nevertheless, I'm (as always) very glad to hear any non-traditional concertina repertoire, so keep it coming
  2. There is HUGE audible difference between aluminum, zinc and brass reeds in "pure testing conditions". For my DIY project I have ordered sample reed from harmonikas.cz with shoes made from three different metals (and also three different aluminium reed "grades") and reeds with same geometry but with different properties of the shoe metal produce completely different sound spectrum. This spectrum can be of course modified to great extent by an instrument maker, but the exact same box fitted with two different sets of reeds will sound different. If your goal in learning to play bandoneon is to play "proper" argentine tango, then you should definately go with zinc plates - this very distinctive sound cannot be imitated even with large accordions with many different reed ranks. But if you are just looking for a good sounding "general use" instrument and prefer bandonion layout/ergonomics over accordion, there is no real point in zinc plates other than personal preference in tone. (But there can of course be further difference in response time and dynamics between different grades of aluminium reeds)
  3. From my experience, clamping is not sufficient - my DIY concertina endplates had warped signifficantly even when screwed to the actual box. Stress caused by unequal drying of wood (or uneven distribution of this stress due to assymetric geometry etc) occurs whether or not the wood is clamped. It will just manifest when unscrewed, but the stress will be present in the wood nevertheless. As a sidenote: plywood warps too, but the amunt of warp for given thickness is smaller in plywood than in solid wood. And from my experience plywood tends to twist rather than bend in single direction (due to crossed grain direction in each layer).
  4. I had a very serious latency problem with the first version of my MIDI software, and found out, that above a certain amount it effectively cripples the ability to play, because sound is generated a bit later than you expect it and this confuses brain too much. From my experience, this critical delay is about as long as it takes your finger to fully press the button (when you have normal force acting on the bellows) - the sound should play no later than when button is fully depressed. Otherwise you have to take this latency into account when fingering (on my Elise this applies to lowest, weighted reeds which are significantly slower to speak than the rest) which requires "forward thinking" and not just following the melody.
  5. Well, this particular discussion, however deep and intensive it is, has very little to do with actual problems arising when building the actual instrument... The "multi instrument" approach which Jake suggested and which is already prooving worthy on the FB group is the main reason why this here forum is not the greatest place for this group's existence. I can remember at least one thread about designing and building a "modern anglo", which was overhelmed by people trying to discourage any modification to traditional Anglo concertina. This, by definition, won't be the case on a forum/group not focused on any single type of free-reed intrument. Similiarly to what you said "I myself don't see attending several forums with roughly the same (or widely overlapping) contents." - so why would a melodeon, bandoneon or accordion maker/player be interested in a concertina forum which even conciders chemnitzer concertinas as "outside of the scope" of this site? And facebook makes it an "automatic" participation for anyone already using this page on a regular basis for whatever purpose they do.
  6. Ron, the whole point of me performing this experiment on the largest reed I have was to try to apply the flow ONLY below to the gap. This reed has a gap of about 1 mm height and tongue thickness at the edge of about 0.5 mm so you can easily flatten the straw below this width. I have performed this experiment once again, this time with bent straw and a lens, so I could observe reed behaviour a bit more precisely. This time I was varying the straw crossection height and here are some additional observations (the bottom edge of the straw is always touching the shoe): - if the straw height is less than the gap height the reed does nothing. - when the straw height reaches the combined height of the gap plus the tongue thickness (probably exceding it a tiny bit), the reed starts to vibrate. - when the straw height exceeds this combined height by a certain amount (but is still lower than double the gap height plus tongue thickness) the reed does not speak (at least not at a highest blow strenght I could achieve) - the assymetry of the flow is to small to propel the tongue. After this experiment my current intuition is that the only part of the reed that is responsible for the ability of the reed to start vibration is the "double V" (*) shaped section just at the tip of the reed and edge of the shoe and the Venturi effect at this small section, combined with bifurcation in the flow caused by the even slightest movement of the tip, deflecting the flow to the upper or lower surface of the tongue. Due to spring forces and tongue momentum this will be an increasing effect. One other thought: until this point we have assumed, that the axis of oscilation is always the same. But I think that it may be false assumption. I think that when the tongue is swinging enough to touch the surface of the shoe and close the gap completely, the pressure acting on the whole tongue surface moves the axis of vibration downwards. And because the pressure acts on the entire surface of the tongue and the initial mechanism acts only on the tip of the tongue, there will be some "wobbliness" in the tongue at this very point - it won't just bend at the mounting pivot point, but also around the center of percussion of the tongue. Think of it: this sudden axis change when the pressure gives the tongue "a kick" occures at the lowest point of the the already established oscilation but is not instantaneous, so the tip is already moving upwards in relation to center of percussion. So when the pressure pushes the tongue as far as it can (and we know from "choking" reed behavior that this is not a lot further than the thickness of the tongue) the initial oscilation, (this time around this new axis) opens the flow on the bottom, the pressure force acting on the tongue drops and the whole oscilating tongue axis moves upwards again. With few further cycles this initial oscilation wears off because the initial mechanism of bifurcation is no longer present (or significant) and the steady oscilation around the mounting point is established without any significant oscilation around the center of percussion. (*) "the double V" shape I think of is the crosssection shape at a tip, because the tongue and shoe are not infinitesimaly thin.
  7. @Dana: your observation may sugest that after those 5-6 cycles the mechanism I seek gives way to the direct acting of the high pressure on the entire area of the tongue pushing it through the shoe. This is also why I was only able to get the reed oscilating above the shoe with the straw blow, getting only a low volume sound.
  8. Well, as I'm more of an experimental than theoretical person, I have just performed a very quick and simple experiment which you can easily reproduce and which I think proove my approach definitively: I've taken my largest reed (the same I've mentioned earlier, which was choking under typical bellows pressure) and a drinking straw (flattened at the end to improve selectiveness of the jet produced), pointed it at the gap (*) and I blew hardest I could. I did manage to start the reed vibration and got a low volume sound. I was holding the reed in my hand in the ambient air, so there was no perpendicular pressure force on the tongue other than resulting from the jet of fast moving air and those two phenomenons I've mentioned eariler (or some additional turbulent effects on the bottom side of the tongue). (*) you have to hold the straw end with your fingernail very close to the gap and tongue.
  9. @ Tom: Of course that all those various fluid dynamics effects come from calculations of the same equation, but used at different scales (both spatial and time) resulting in looking at a different geometry and airflow. I think that our missunderstanding comes from looking at the reed tongue at two different scales. You look at the reed as a divider between high pressure reservoire and low pressure reservoire and try to describe it at this "large" scale of an airflow. I on the other hand, focus only on the flow through the gap "magnifying" it. I'm not particularily interested in pressure differences between the bellows and the chamber and the steady oscilation phase, because I try to understand only the first cycle of movement, which we already agreed cannot be explained by this "large" scale (P1-P2)*A approach. It should be clear by now, that I think that the reed would close even when subjected to a very selective jet of air pointed only at the gap (prior to introducing this jet, the reed as a whole subjected only to ambient air pressure, equal both above and below the tongue).
  10. To be clear - I think that at the later stages of the reed oscilation the effects I have described coexist to some degree with the direct effects that the pressure gradient has on the oscilating reed.
  11. Tom, all theoretical papers I've found on free reed analysis skip the starting period and focus on sound generating properties of steady oscilation. I also think, that slow motion, smoke airflow analysis is the only logical step in verifying my assumptions. Unfortunately I'm bound by the capacities of my workshop here which does not include high speed camera I'm also aware, that my explanations weren't as clear as they should be, and there are two main reasons for this: first is the language barrier and the second (more important) is that my times at university are long past and I haven't done serious math for more than a decade now. This is why I can only operate on simple illustrative experiments, observations and intuitions and must withheld from throwing any calculations into this discussion. Instead I did some digging and I think I have finally found a well-described principle that I was trying to ilustrate with my paper experments. It's called Coanda effect http://en.wikipedia.org/wiki/Coandă_effect and describes the tendency of a fluid jet to be attracted to nearby surfaces and is one of the fundaments for the lift force generation and numerous other fluid flow phenomenons. This combined with the third Newton's law makes the tongue to be atracted towards the jet as well and is what I think draws the tongue into the shoe at an early stage of the oscilation. The second principle which I have tried to describe with "the paper corner reed" example (in the part of airflow acceleration) is Venturi effect http://en.wikipedia.org/wiki/Venturi_effect which speeds the airflow and significantly lowers the pressure locally at the gap below P2, and in consequence increases the force generated by Coanda effect. Both of the effects above are generated only dynamically and are significant only when there is fast enough airflow, so as soon as the gap is closed (*) the tongue can spring back upwards against the pressure gradient. Because there will be some time needed for the airflow to reestablish after reopening of the gap, the tongue can have enough time to swing higher than initial position. In my opinion this combined effect is present also at a stable stage of the reed oscilation. This effect can also be present at the second (and third) point in the reed cycle, when the tongue crosses the bottom of the shoe, creating another gap - this time with the force acting upwards. But those both statements heavily depend on whether or not there is enough time for the steady jet to be formed at those later stages of tongue oscilation. Those effects are of course dependand on pressure difference P1-P2, tongue area and all sort of reed parameters, so they will be proportional to them in some way or another, so those "microscopic" effects may be in fact omitted in "macroscopic" description of the stable phase of reed oscilation, when the focus of description is mainly on acoustics of the free reed (as is done in all reed-related articles I could find on the web). I hope this time my point of view is finally clear enough to be seriously considered (either as true or false) as a coherent "theory" based on actual physics (*) there will probably be a slight delay between cuting the airflow and upward acceleration of the tongue because of inevitable turbulence below the tongue caused by a sudden cut-off of the airflow.
  12. This is exactly why I think that (P1 – P2)*A is not a maximum force acting on the reed and an airflow through the gap must create force larger than this - you are seeking an additional mechanism that causes an amplified return in the first cycle, I seek the different mechanism which draws the tongue into the shoe in the first place, so the return mechanism is plain and logical. This force created by the gap airflow and it's relative value to the pressure applied to the tongue is easiest to observe on the lowest/largest possible reeds as the scale and frequency of movement is observable with a naked eye. If I experiment with my lowest reed on my tuning rig, this is what happens: 1) if I act on the bellows with normal force (pulling on the bellows, so I can observe the tongue motion above the shoe) the tongue is pushed into the shoe (just the thickness of the tongue below the edge, so the whole reed is flat) by the (P1-P2)*A force and does not speak, it acts only as a pressure valve. (by "normal force" I mean the force that makes treble reeds speak) 2) in order to make it speak, I must start the airflow through the gap with a much lesser force on the bellows (so that (P1-P2)*A is to small to draw the tongue into the shoe and in the same time is too small to keep it inside on the "agaist the pressure" part of motion). The tongue start to vibrate (at the stage in which it does not even sink into the shoe with all it's thickness and almost all of the oscilation happens slightly above the shoe) and only then I can increase the force on the bellows to make it louder. (I can recreate this reed-starting behaviour with weights attached to the bellows, so the eventual unsteady motion of the hand is not a factor in this) Another "paper experiment" for you to ilustrate that lift is generated: take a small piece of paper (I have used 5x10cm strip) and place it so it is horizontal (rest it on your finger) and has one (short) edge firmly held against your lower lip and then blow on it. As long as you blow there is an airflow speed difference between the upper and lower sides of the paper, so you can take your figer away and the paper will stay horizontal. The curvature of the paper is not important, it does not need to be an airfoil - an airfoil shape is necessary to divide the single pressure enviroment into two enviroments of different pressure but in this case we divide the enviroment by introducing the selective airflow by blowing just on the upper side(*). As soon as you stop blowing, the paper bends naturaly downwards, but you can lift it again by blowing (in this "freely hanging" starting position it does resemble an airfoil at the begining, but it becomes more flat the harder you blow and this shape is not essential to lift the paper as shown above in "resting on the finger" starting position). If you look at the closeup of the reed tongue at the gap, it looks very similiar to this experiment: due to the tongue/gap/shoe geometry there is significant airflow only on the single (lower) side of the tongue. And my above example with the low reed shows that this effect occur at pressure lower than needed to push the tongue into the shoe and that this is essential for the reed to speak. So I must disagree with you Tom on your statements that my illustrations are incorrect. My interpretation seems to be coherent with all different reed types: free, beating and double (and double oboe reed is the most close realisation of the "two sheets of paper" experiment, just with the hinge points on the oposite ends of sheets). And especially beating and double reeds cannot be explained by the approach in which (P1-P2)*A is the largest acting force, as this would just cut the airflow completely and hold the reeds closed as long as there is high pressure acting. And as you Tom admit, your interpretation fails to explain how the reed goes back against the pressure to higher position. Mine may of course be entirely wrong, but it does at least explain this and can be illustrated by all sort of different experiments. (*) to be perfectly correct there is a secondary airflow on the lower side of the paper to ensure the continuity of the flow speed gradient across the enviroment (the flow is laminar, no turbulence is created or necessary), and is caused by the upper airflow, but it is much slower than the upper flow.
  13. Not to start any further debate, but just to clarify what I had in mind all this time, I have finally found a proper english name for what I have called a "suction effect" - I have previously used the direct translation from polish "zjawisko przyssawania" but it is called a Bank Effect in english: http://en.wikipedia.org/wiki/Bank_effect (as you can see now it is not a partial vacuum which makes drinking with straws work). This was my first physics debate in english and I can only apologise for not using proper english terminology (I have tried to find this name then, but have failed to…)
  14. First, the price: cost of a set of 62 DIX reeds from Harmonikas.cz for my Hayden was 400 euros. When it comes to wet/dry tuning, then it is a matter of tuning, not changing plates - dry tuning is just two very closely tuned (a spot-on or couple of cents apart) reeds playing the same note at once, while wet tuning are those same two reeds when tuned wider apart. But it is not a simple matter of changing the reeds if you want to modify the layout. You have strict chamber sizes on the other side of the lever when you press a button… So it is possible to make unisonoric instrument from bisonoric one, but the resulting layout could be even more bizarre. Reeds come in sizes, here is a size chart for harmonikas.cz: http://www.harmonikas.cz/admin/files/ModuleText/16-sortiment-sizes.pdf So if you want a strict layout after your modification, it might need tampering with chamber sizes also. That can lead to a mayour rebuild on the reedblocks/reedpan and depending on instrument may or may not be easy or even possible.
  15. Depending on your budget and dedication, you have three options available: - starter Elise from Concertina Connection at 425$: 34 button, limited instrument, but perfectly capable of learning all of the Hayden techniques on it. And it can be traded in for a discount when upgrading to either of two of the following: - Concertina Connection Peacock at 2900$: 42 "almost standard" instrument. Not perfect because of those missing 4 buttons, but the cheapest, fully usable instrument. - Morse Beaumont at 3950$: 52 button instrument, the highest range available "off the shelf" with some very good opinions on the build, tone and action. All of the above are hybrid concertinas, with Peacock being the only one with flat mounted reeds (Beaumont has a mix of both reedblocks and flat mounted reeds). For the cheapest, traditionally reeded instrument you have to pay almost 6k$ and wait 6 years... You could also contact Bob Tedrow and ask him if he's willing to build one, he has done it before. There is a very little chance for finding something larger/older/more traditional second-hand, there were only few offers of used Peacocks recently.
  16. The answer is beating reed. The difference is that in free reeds, the tongue swings freely through the opening in the shoe, while the beating reed is slightly larger than the opening that it's fitted onto so it is beating against it to cut the airflow.
  17. Thanks for that! I didn't knew that there was any recording of this tune on concertina (there is a typo in the name of it on YT site, it should be "ostatnia niedziela" so search engine sadly doesn't return this recording). It is one of my "tunes to learn" when I'll finaly have an instrument with all necessary accidentals and range and one of my all time favourites. I have even suggested it a while ago as a TOTM material. It is very popular amongst polish accordeonists and a song with a long (and sad) tradition. It's telling a story of a break-up and it is said that this song has been often requested from bands by men (officers mostly) just before commiting suicide (because of a broken heart) in the interwar period.
  18. While the options are certainly limited, complicated, and somewhat formidable undertakings, they do exist. Despite the liklihood of incurring the wrath and criticism of the purists here, I will share with you that my two Jeffries duets are two such examples. The 58-button was converted from a C-core duet to a Stark layout and the 62-button A-core duet was converted to a C-system CBA layout with extraordinary results. This is certainly no undertaking for the faint of heart. It requires the skill, expertise, vision, and willingness of a superbly qualified individual like Wim Wakker, substantial planning and engineering, finding and acquiring an instrument with the proper range of notes that can be suitably adapted while preserving its originality and maintaining its fundamental integrity, the willingness to invest the necessary funds, and the ability, as Lady Macbeth so aptly puts it, "to screw one's courage to the sticking place." It takes time (months, really) to properly analyze and suss it all out and determine the feasibility. Then it requires far more time to complete the work properly as it involves a meticulous and sophisticated series of intricate processes. But in the case of these two concertinas, the risk paid off and produced a handsome reward - two extraordinary concertinas that were previously lying dormant are now readily playable and regularly fulfilling the purpose for which they were originally constructed. I meant "no valid purchase options", my imprecision... Of course you can always buy a different system concertina and convert it to your liking (the route suggested by OP and the one you had taken) or build one from scratch yourself (as I and few others have chosen to do). 5 years of waiting is long enough time to even aquire and train necessary skills. This is true even if you have no background in any craft at all but you are dedicated and have enough spare time and are not easily discouraged by inevitable and numerous smaller or bigger failures along the way. And in my case this "from scratch" aproach is even saving me money, as I desire a large box but I'm happy with a hybrid, so my "budget to beat" is a pricetag on Wakker W-2/H-2, the only 60+ Hayden box currently out there. With your taste in systems, you had certainly even more limited choices than Hayden players have. And your story is a great example of the oposite side to a "moral dilema" that Stuart has raised - you have converted a very rare instruments into ones even more singular and far more usefull to the owner. A sort of "player before an instrument" approach, which I share deeply.
  19. I do use very straightforward and cheap solution with my Elise. I just put some thin foam sheet in the "fretwork" and it dampens the volume significantly (around 15-20 dB), with only a slight effect on the tone. One important thing - each such "insert" must be cut roughly enough for the air to leak slightly through each of the existing fretwork holes. To tight fitting will cause the reeds respond poorly and sound weak. The added bonus of such baffles is that there is less air consumption, so it is easier to play rich harmonies with the small bellows the Elise has. But be warned: as this is of course a fully reversible process it does teach you different habits (you won't be able to play some tunes with same belows direction phrasing with and without the baffles)
  20. You're welcome Wolf, and thank you for expressing your appreciation of the effort taken
  21. What I understand from "your physics description" is that in your opinion such terms as lift (your "partial vacuum formed due to airflow") which is the common and precise level of description on academic level of fluid mechanics and aerodynamic studies, are a jibberish, non-physics and unnecessary complication in trying to describe phenomenons emerging from dynamic motion of a fluid flowing around solid objects… And I understand, that there is the same principle behind this approach, as in centrifugal (aparent) vs centripetal (real) forces. But your refusal for aknowledging their existence as useful descriptive tools is a mystery to me. Even if they answer your questions precisely, are constructed in a strict, physically proper way with a clear underlying mechanism (in much simplification, the Bernoulli's principle in case of lift), and solve the mysteries of observable reed behaviour. And yes, dynamic pressure (lift force) on the low pressure side of the tongue is what drives the oscilation, which I was telling you from the very start of this whole debate. And obviously, there is no difference between raising the tongue a bit or filling the shoe a bit to create a gap - the relative position is what matters. As long as there is assymetry in relation to the tongue resting position, the reed will speak as the airflow will be as in my fig.1 image. If I can recall correctly I have even saw a concertina or harmonium reed filled this way. "since it requires that reed be sealed off from ambient air pressure for it to work" - you have clearly never seen a reed tuning rig, have you? Or even took a reed, placed it between your lips in front of a mirror and draw breath through it? "If the amplitude of the oscillation is of the order of millimeters as you say, the design won't work with a single cutoff point on the low pressure side." It is and it works just fine and you should finally get "your physics" straight with the observable facts... This is my last post in this lecture, I wish you best of luck with your understanding how the reed works. Feel free to disprove my statements by actually building a bidirectional reed of your design. [edited to add some clarification to the first paragraph]
  22. @ Chris: But all his tools listed on his webpage work in connection with a hobby-level Dremel multitool. Of course his rigs and setups are rigid, durable and clever (but sometimes "an overkill" for a one-time use, like his bellows mould or hexagonal cutter or slant tapering rigs, and could be easily substituted by one, versatile milling machine with compound table and tilting capabilities and much simpler add-ons, or even by hand tools in some cases. Of course they are more than justified if he is thinking about making more than a single concertina with them), nevertheless they are anything near industrial level pieces of machinery, and are a lot easier and cheaper to aquire/make than even the home-grade CNC router that Don have mentioned (I should have quoted the exact Don's sentence I was reffering to). But I indeed may have a quite biased view of what a "hobby workshop" looks like, because I consider myself a hobbyist "object maker", but have invested a lot of time, money and effort in completing/designing my workshop and tools...
  23. No offence intended, but with this post you have again proven, that you still know very little about observable reed behavior… Some facts then, that you can observe even with a naked eye, actually looking at a sounding reed: Low A=220Hz reed on moderate volume (gravitational pull on the bellows only) has an amplitude of tongue movement of 5mm (10mm total travel) and to a naked eye this amplitude is symetrical and I don't think that there is any significant assymetry even when measured with apropriate instruments. Plate thickness is usually around 2mm, so with your symmetrical design there would be at least 1mm of tongue movement outside the shoe at each side (if your reed would work) . And this is still at moderate volume. Largest bass reeds can have an aplitude easily exceeding 10mm. What you have described in your opening post, about the lift force created on a tongue is finally true - that the tongue is more similiar to a plane wing than a pressure valve and static pressure of the higher pressure side has neglectible direct effect on it's movement. But after carefully analysing your design, I must say that you forget about orders of magnitude of involved effects and in your latest post strongly overrate the effect of a static higher pressure on the tongue. Again, look at the actual reed - even when no leather valves are present to cut unwanted airflow, only the sounding side reed moves, the other just leaks air, it does not bend in any signifficant way. With your model it should bend proportionally to the pressure gradient in the same way as the sounding reed. Please understand, that the whole process of sucking the tongue into the shoe and resonant amplification of oscilation happens at this tiny area near the point on the tip of the reed tongue and the only significant aerodynamic force act only there. Pressure gradient is needed only for creating wind, which moves almost parallel to the shoe and reed tongue "meeting point". What I have overlooked in my first reply to your proposed design is the flow which you think will drive this design in the first place. Now I think that it won't even start or will have a very slight vibration only. Here is a quick picture, that may help you understand the relative values of forces involved, and an actual airflow shape. Little grey arrows represent the higher pressure acting on entire tongue. Blue arrows represent the airflow, which is faster in the areas when the lines are closer together. Green arrows represent the lift force, resulting from the airflow. Fig.1 represents the typicall reed in it's starting position. The lift force is orders of magnitude higher than the force from pressure gradient. The same effect would occur in your design on the upper shoe-edge crossing point if somehow your reed could start. Fig.2 represents your design. You can see how the lift is created on both sides of the tongue, with values much smaller that on the "classic" assymetric reed. The similiar forces (however even smaller) are created in normal reed due to flow through tongue fiting tolerances. See how the upper flow creates a significant dampening force, which I have mentioned earlier. Fig.3 represents an additional lift force created when tongue passes through the shoe. It is again working towards the resting point and propels the resonant oscilation slightly. It is weaker than on the upper side of the reed, because airflow is not instantaneous and it works within a shorter time than on the upper side. To illustrate orders of magnitude of involved forces, I have another quick and simple experiment for you. Take a piece of typical printer paper. Place it at some distance from your mouth, with one of the corners pointing upwards at mouth level (with corner point at a level of the top of your upper lip), holding it stretched firmly in two hands about 5-10 cm from the corner. Then start blowing gently, silently and steady through a small hole between your lips (so the pressure gradient between your lungs and ambient pressure is the same throughout the experiment) and at the same time start closing the paper to your mouth. At some point you will start to hear the slight noise of air accelerating due to obstruction of pathway. Keep closing the paper slowly to your mouth. There is a very distinctive moment (at few mm from the mouth), when closing the paper even slightly closer will rapidly change the direction of the airflow (down along the paper) resulting in a gentle "pat" of the paper corner on your lips. This is the moment when gap suction aerodynamic effect occur, sucking air from above the corner, creating dynamic underpresure on the closer surface of the paper, moving the paper and closing the gap. Note that there will be no audible change in noise volume (but there will be change in tone from a high pitch whistle to a lower pitched noise due to paper dumpening energy). Then fiddle around with blow direction, paper position and blow strenght and you will find a "sweet spot" when a paper stretched between hands will start flapping or even sounding with a reed-like buzzing sound (in addition to a whistling noise of airflow). You can observe that the paper movement at this distinctive point is much stronger that even slightly further away and that your blow force is bending the paper only slightly outwards. This is the physics of a beating reed ilustrated in a simplest experimental form. The physics of the free reed is different in details but general principles and involved forces remain the same.
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