mlefree
108 posts
Jul 24, 2013
12:36 PM
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There's a very cool thread going on about bending:
Iceman's Bending Articulations
I didn't want to hijack this thread but the subject of bending is so essential to playing the harmonica that I thought I would once again mention Helmholtz Resonance (Helmholtz was a 19th century German physicist). Bear with me now...
The idea is simple really, so that non-physicists can easily "get it," but it is based in enough mathematical physics to satisfy the most rigorous physicist or mathematician.
Helmholtz Resonance is what happens when you whistle, when you blow into a bottle or when you play a musical instrument like a guitar or a... harmonica. The bottom line is that the size (volume, dimensions...) of a resonating cavity determines the frequency at which the air inside it will vibrate. That is called the natural frequency of that cavity.
Helmholtz invented his resonators in the course of his acoustical experiments. They are simple brass ear syringe looking orbs with small holes or ports that he could put inside his ear to hear the sound vibrations inside.
For the curious, here is a page that explains Helmholtz Resonator in detail:
Helmholtz Resonators
For the more practical, this video shows the natural frequency of a large Helmoholtz Resonator (HR) being "excited" by a tuning fork. The scientist then tries to excite the natural frequency of a smaller HR using the same tuning fork. Notice that the smaller HR will not resonate at its own natural frequency, but just the frequency of the tuning fork, albeit at a far lower volume.
Message: you can't make a chamber resonate well at any but its natural frequency.
This relates to playing harmonicas in several ways because your airways act as an HR. We all know that one must adjust the size of their oral cavity to the various keys of harmonica. A wide-open mouth, "yawning" throat and expanded chest works great for lower key harps but not so well for higher key harps.
The take-away message for all this is that HR also relates to bending. A player must "tune" the size if his/her oral cavity, the extent to which the throat and chest are expanded to the "target" bent note just as s/he does to different key harps.
This is why beginning players have difficulty bending lower keys. They enter the world of bending using the position of their tongue using vowel articulations like "OOOOOh-EEEEE" and do fine until they get to the 3-hole or lower when they hit a dead wall (I know I did, and my all students do...).
That's when they need to learn to use throat resonance to get down with those lower notes. And HR is why.
Thought at least some of y'all might find this useful.
Thanks for humoring me,
Michelle
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email: mlefree@silverwingleather.com
Last Edited by mlefree on Jul 24, 2013 12:46 PM
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Pistolcat
457 posts
Jul 24, 2013
12:56 PM
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Very nice post! Thank you. Perfect thread for all beginners here to ponder.
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Pistolkatt - Pistolkatts youtube
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BronzeWailer
1089 posts
Jul 24, 2013
3:11 PM
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Interesting. I wonder if the adjusting the position of the soft palate plays a role in all of this or is it a minor adjustment in the overall context? I will try experimenting myself but would be interested if anyone has opinions on this.
BronzeWailer's YouTube
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dougharps
425 posts
Jul 24, 2013
3:45 PM
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My favorite Steve Baker video addresses this:
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Doug S.
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The Iceman
1040 posts
Jul 24, 2013
3:56 PM
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Once again a debatable and another approach to bending.
Michelle sez " A wide-open mouth, "yawning" throat and expanded chest works great for lower key harps but not so well for higher key harps."
Not really understanding nor knowing what an expanded chest is. I do know what expanding the diaphragm does.
As to the "yawning" throat, my approach is that "pre-yawn attitude" that never changes as well as a sorta wide open mouth....even when playing higher harmonicas.
The higher the harmonica, the more I move forward my target spots (roof of mouth) towards which I "aim" that lump in the tongue.
Many different paths, for sure.
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The Iceman
Last Edited by The Iceman on Jul 24, 2013 3:58 PM
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STME58
504 posts
Jul 25, 2013
12:35 AM
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I just did some quick calculations of the required volumes for Helmholtz resonators from A3 to A6 using a 6mm x 6mm x15 mm neck, about the size of a harp comb channel.
The volumes I got ranged for 2CC for A6 to 145CC for A3.
This is making a LOT of assumptions because a human oral cavity is not a closed rigid chamber and having a reed in the neck of the chamber would effect the resonance. That said, it does seem these volumes are not to far off the size an oral cavity can be adjusted to. I also played around with the numbers and found them quite sensitive to the length of the comb slot. Shorter slots require a larger volume to get the same frequency. Shorter slots for higher pitches keep the resonating chamber volume requirement more constant.
I wonder if something like a Helmholz resonantion is going on and tongue motions Iceman describes are enough to tune it.
What Steve Baker said in the video makes sense to me. Shape your vocal column to whistle the note you are playing and you will be in resonance with the reed, no calculations necessary!
Last Edited by STME58 on Jul 25, 2013 12:42 AM
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The Iceman
1042 posts
Jul 25, 2013
4:27 AM
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Helmholtz sez " the size (volume, dimensions...) of a resonating cavity determines the frequency at which the air inside it will vibrate. That is called the natural frequency of that cavity."
I can see this when blowing into a bottle, but am having trouble understanding how this works with a vibrating reed.
I can hold a harmonica out the window of a moving car and the reeds vibrate. The chamber resonating is the whole world, sorta.
You can take a bellows and direct it's point into a harmonica chamber, pump it and the reed will vibrate.
A vacuum cleaner nozzle can suck the air through a harmonica and cause the reed to vibrate.
So, how much of this concept is really affecting harmonica reeds?
Any new insight is appreciated.
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The Iceman
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Pistolcat
463 posts
Jul 25, 2013
7:33 AM
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I can get sound out of my harmonica reeds holding it out the car window sure, i can get it to sound whacking it against my palm too. The tone will be poor though. The idea of a cavity that resonates and enhance the reeds' sound to give us that rich tone is almost an axiom. We can even change the pitch by resonating another note. We do this by changing the size and probably some other variable in the (oral) cavity by raising or lowering our tongue or widening or shrinking our throats. I believe that this "other variable" (if there is any) is less important than the size of the cavity and apparently the avilable science backs this.
This is why I can say "Both Iceman and Harpdude are completely correct on how to bend with good tone even though their method differs".
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Pistolkatt - Pistolkatts youtube
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The Iceman
1044 posts
Jul 25, 2013
7:53 AM
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I've kinda come to the conclusion that Harpdude and I are talking about the exact same thing.
Only difference is that I focus on tongue placement while he focuses on throat.
I've found it easier to create controlled bends by aiming the tongue at a target point while keeping the throat in pre yawn attitude rather than asking the throat to do all the work.
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The Iceman
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S-harp
151 posts
Jul 25, 2013
8:04 AM
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Oral cavity, throat, lungs ... and don't forget, the nasal cacity and the sinuses ...
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The tone, the tone ... and the Tone
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Pistolcat
464 posts
Jul 25, 2013
9:50 AM
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@iceman- exactly! There may be many ways to skin the cat but it is still the same cat.
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Pistolkatt - Pistolkatts youtube
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mlefree
109 posts
Jul 25, 2013
10:58 AM
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What Helmholtz, Baker and I are saying is that the oral cavity and airways are the resonating chamber for both whistling and playing the harmonica. Further, that adjusting the size of your throat via the "yawning" muscles, jaw position and soft palate position, one can enhance the ability of the vibrating reeds (chopping the air in and out of the reed chamber) to resonate to a target note.
This ability to adjust one's resonant chamber manifests itself in several ways in terms of playing the harmonica. As Steve Baker suggests (gotta love Steve Baker!), one can improve one's tone and enhance one's bending skills and resulting tone. I'll add another -- getting a deep, bluesy vibrato. A player can control his/her vibrato in several ways, each in accordance with the idea of natural frequency. Tongue vibrato, jaw vibrato and diaphragmatic vibrato all subscribe to this theory.
Knowing this and exercising those pertinent muscle structures in the mouth, tongue, back of the throat and in the diaphragm can give a player additional tools in his arsenal to enhance the quality of the sound they produce.
Note that I said add to their arsenal. I am not saying that one method of bending or producing pleasing tone is better than another. Quite the contrary, I think they are all complementary. For me, bending higher tones is best controlled by my tongue. I leave the tip of my tongue anchored at the back of my front teeth (letting it wag or protrude into the oral cavity degrades tone, IMHO). Much as Larry describes, I move the "arch" of my tongue from front to back as the note gets lower. This works great until I get to a lower key harp, say A or G, and want that deep 3-hole bend to ring out. I cannot do that without lowering my jaw to its max and using by yawn muscles to open up the back of my throat and being very conscious of the position of my diaphragm.
Others may differ. With all due respect to the Master and former World Champion and one of my favorite contributors herein and elsewhere, The Iceman hisse'f, I can't understand how anyone can bend with good tone, say, low C or D 3-holes on down with just his tongue, leaving his yawn muscles and diaphragm out of the picture entirely. I know I can't, but that's just me. :^)
Anyway, I'm not here to argue or debate. I just thought another viewpoint with some solid scientific and musical knowledge behind it might help understand what's happening "behind the reeds." Works for you, great. If not, don't get hung up, move on to the next step your journey learning to play the tin sandwich well!
Thanks, Michelle
BTW, who is HarpDude?
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email: mlefree@silverwingleather.com
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The Iceman
1047 posts
Jul 25, 2013
11:13 AM
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Michelle sez "With all due respect to the Master and former World Champion and one of my favorite contributors herein and elsewhere, The Iceman hisse'f, I can't understand how anyone can bend with good tone, say, low C or D 3-holes on down with just his tongue, leaving his yawn muscles and diaphragm out of the picture entirely. I know I can't, but that's just me. :^)".
I don't think I ever suggested leaving pre yawn attitude out of the equation.
However, in my years of developing teaching methods, I did arrive at the ability to create all the bends necessary with my jaw closed....teeth almost touching.
I did this to try to isolate exactly what is needed to create bends.
Of course, pre yawn attitude, jaws open enhances the tone, but I concluded that these were separate entities from what is needed for bending technique.
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The Iceman
Last Edited by The Iceman on Jul 25, 2013 11:15 AM
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mlefree
110 posts
Jul 25, 2013
11:13 AM
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Ice, if I may...
Your examples all conform to the theory Helmholtz put forth, given that the reed chopping the column of air flowing in and out of its chamber are the source of the sound vibration.
The "world" isn't a chamber, so there is no resonance. All you are hearing is the sound source.
The bellows is a chamber so what you are hearing is the sound source as well as the sympathetic vibrations it has "excited" in the air inside the bellows. I've never seen a harmonica bellows, but I would posit that certain notes would sound louder than others, and that the reason for that would be that the frequency of the louder sounding notes would better match the natural frequency of the bellow's chamber.
Yes, a vacuum cleaner will also cause the reeds to sound, via the air column chopping concept. But there would be little if any resonance in the tubes leading to the motor.
The point is that resonance isn't a phenomenon of the reeds themselves, but of the resonant chamber behind them.
Hope that helps,
Michelle
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SilverWingLeather.com
email: mlefree@silverwingleather.com
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mlefree
111 posts
Jul 25, 2013
11:29 AM
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OK Larry, I don't understand how you can do it but I certainly don't doubt you.
It's just that I wouldn't want the new "benders" out there to think that your way is either easy or the only way. I know that in my learning experience I hit a total dead end brick wall with bending and trying to maintaining good tone on lower key harps until I discovered how to "throat bend." I truly believe it is the next step beyond "ooooh-eeeee" tongue articulation method of teaching bending.
Obviously, your mileage varies. :^)
Respectfully yours,
Michelle
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SilverWingLeather.com
email: mlefree@silverwingleather.com
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STME58
505 posts
Jul 25, 2013
11:34 AM
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“So, how much of this concept is really affecting harmonica reeds?”
This is exactly the question I have. The preliminary math tells me it is likely to be part of the effect. The volume required is in the right range and small changes of volume are needed to change the Helmholtz natural frequency by a half step. I am sure this analysis has been done more thoroughly by others . I am contributing only to my own understanding, not the general body of knowledge. I was surprised to see how sensitive the resonant frequency would be to the length of the comb chamber. The math I did showed it would be advantageous to use shorter chambers for higher notes, that again points to a Helmholtz effect contribution to the tone of the harmonica. Has anyone tried a harmonica where all the comb slots are the same? If so, did you notice a difference?
The main effect of the harmonica pitch is that of a vibrating cantilever beam. If I measure a reed with calipers and a micrometer and put the length, thickness, density and modulus of elasticity into the cantilever beam equations, I get a very accurate estimation of the frequency that reed will sound at when plucked. If I put these parameters into a CAD model and do a modal analysis, I get an accurate indication of where the reed will break due to fatigue. It is quite clear that the vibrating beam mode of the reed is important to the frequency of the sound. My understanding of the mechanism of creating the acoustical vibrations is not mainly from the air moved by the reed like a guitar string works, but by the reed working like a valve to let little puffs of air out of the pressurized reed chamber (similar to how a siren works).
The math can be fun, and useful to an instrument designer ( I believe I saw in a Seydel video that they do have engineers on staff). I will leave you with this story from my past as to the math’s relevance to playing.
A group of us were standing on the college lawn talking after just coming out of a calculus lecture on how to compute rotational inertia. One person said something like, “let’s see, due to conservation of angular momentum, if I can reduce my rotational inertia by bringing the parts of my body closer to the center of gravity, I might be able to spin fast enough (pause for deep thought) yea, based on what we just learned I think that will work!” He then proceeded to do a standing backflip and land on his feet! It was hilarious. The reason it was so funny was that we all knew that his new mathematical knowledge had nothing to do with his ability to execute that backflip.
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The Iceman
1048 posts
Jul 25, 2013
12:16 PM
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Michelle sez :It's just that I wouldn't want the new "benders" out there to think that your way is either easy or the only way."
Although I never claimed that my approach is the only way, I don't understand why you wouldn't want new "benders" out there to think that my way is easy.
It is the easiest way I've found (after 15 years of teaching) to get beginners to bend to pitch within one or two weeks.
I always work with the students with the "it's really a lot easier than you think" philosophy. If someone wants to insist that it is hard, than so be it for them, but not for those that I teach. As a matter of fact, I do a little psychological self dialogue education with students - "as you thinketh it should be, so shall it be" kinda stuff.
I help them to change their way of thinking as well as educate them to accept fast, easy and a short cut to the top of the mountain.
I've tried to outline everything in forums, but there is really no substitute for live teaching where I can demonstrate with other visuals exactly what is going on with the tongue.
It's so much fun and works so fast that (and I never would have believed it), I actually prefer to teach those that have never played diatonic.
Those that have spent x number of years playing usually have a lot of built in bad habits and/or concepts that they really don't want to release (having "invested" so many hours of their time).
I've actually found that those that resist my direction the most are those that had to spend x number of years with the "keep at it and eventually you will figure it out" approach.
They don't seem to like the fact that it can be done so quickly and easily when they had to work so long and hard at it.
Basic human nature.
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The Iceman
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wolfkristiansen
196 posts
Jul 25, 2013
3:25 PM
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"It would be advantageous to use shorter chambers for higher notes, that again points to a Helmholtz effect contribution to the tone of the harmonica."
I was just discussing this with James Cotton and Billy Boy Arnold. They agreed.
Cheers,
wolf kristiansen
p.s. Just having fun with y'all. Don't jump on me.
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mlefree
113 posts
Jul 26, 2013
10:19 AM
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Iceman, I'm not trying to dispute your methods or your success with your students. All I am saying is that ~I~ cannot do all the bends I need to do with changing only my tongue shape and motion. I need to orchestrate the whole package, tongue, jaw, soft palate, yawn muscles and diaphragm to play with the bending accuracy and resonant tone I strive for. I say strive, because for me it is turning out to be a life-long pursuit to play the short harp well.
Michelle
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SilverWingLeather.com
email: mlefree@silverwingleather.com
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The Iceman
1053 posts
Jul 26, 2013
11:37 AM
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Michelle...
If you want a short cut, take a few lessons with me :)
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The Iceman
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mlefree
115 posts
Jul 27, 2013
10:38 AM
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(Chuckling...) Larry, I thought you'd appreciate my little "Alley Oop."
And, if I could afford it, I'd gladly take you up on your offer!
Thanks,
Michelle
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SilverWingLeather.com
email: mlefree@silverwingleather.com
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Milsson
76 posts
Jul 27, 2013
2:03 PM
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This is really interesting! We all know that a single note consist of a sine wave but it also has it´s brothers and sisters called harmonics.
I believe that the "tone", thin and BIG, is a way of tuning your mouth to the freq. of that harmonic.
I´ll explain more:
If you pluck a string that´s tuned to A2ET you will hear a sine wave at 110HZ but you will also hear a series of harmonics.
110hz A2------------------------------------------------------
220hz A3 2nd harmonic an octave higher
330hz E 3rd harmonic----------------------------------A major chord
440hz A4 4th harmonic two octaves higher
550hz C# 5th harmonic------------------------------------
If you would tune your helmholtz resonator aka your mouth to say 330hz that harmonic should be heard clearer and thus create a different "timbre" of the note.
Am i right or is this just a theory?
I believe i can feel when I'm hitting the sweet spot in the "cavity tuning" when I'm playing my G and lowF harmonica. The cover plates vibrates more and i get a tingly feeling in the back o my mouth/throat when i really try to open up and go big.
Last Edited by Milsson on Jul 27, 2013 2:05 PM
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Milsson
77 posts
Jul 27, 2013
2:34 PM
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Found a video:
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STME58
506 posts
Jul 27, 2013
9:12 PM
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Pistolcat,
If the cat Iceman and Harpdude are skinning is Schrodinger's cat, it all starts to make sense! ;-)
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STME58
507 posts
Jul 27, 2013
9:28 PM
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Milsson,
I suspect you are right. I think the tuning fork and Helmholtz chamber video, Steve Baker's shape your mouth to whistle the note, then play the note and your description, are all ways of describing the same thing. I thought it particularly interesting when Steve set his mouth the whistle a note not in the harmonic series of the note he was about to play and the harp barely sounded.
I also think this may relate to the "Why reeds break" thread. If you are matching resonances, you are going to get a lot more volume with the same breath force compared to if you are not matching resonances. The volume of the harp may be able to increase without the mechanical amplitude of the reed vibration increasing if you match the resonances.
A co-worker told me Friday he got an FFT program working reliably. If so, I can use it to analyse sound files to break the sound down into its harmonics like the video above. If I get it working I will post results of harp sounds. I will also be doing some high speed camera work next week. I may stay late one night so I can point the camera at my harp and see if I can get any interesting video to go with the sound files.
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Milsson
78 posts
Jul 28, 2013
9:58 AM
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@STME58 Wow!! If i got my hands on a high speed camera i wouldn´t do anything else. It´s soooo cool!
What I would like to see photage of is a valved bend and that squeling noice that sounds when you do a overblow on a suzuki or lee oskar harp. If you cover the blow note with your finger and bend you should get a "valved" bend.
It would be fun to compare the harmonics from a sax with a harmonica. It´s a reed instrument but works in a different way.
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mlefree
118 posts
Jul 28, 2013
12:32 PM
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STME58 and Milsson, you are two cool dudes!
STME, you must be a mechanical engineer! :) Fast Fourier Transform, a key that unlocks many scientific doors. I used to use it in medical image processing, 2D in that instance. Decomposing harmonica sound waves looks like a very interesting project. Please keep us posted!
And Milsson, I think you are definitely on to something there. Overtones make powerful contributions to an instruments sound. And donchya just dig Steve Baker?
Thanks,
Michelle
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SilverWingLeather.com
email: mlefree@silverwingleather.com
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STME58
509 posts
Jul 31, 2013
1:17 AM
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This thread got me thinking and researching. I was wondering if there were any articles in Smithsonian Magazine on the Harp like I have seen on the Violin. I found some historical articles on harp but nothing mathematical. I did see a phrase in the latest violin analysis that got my attention, "One distinguishing characteristic of a Stradivari violin is a consistent volume of air within it, which can affect tone quality." Sounds like Helmholtz here. The violin can not change volume (space, not loudness) like the harp player can so Stradivarius must have hit on the optimum volume for the instrument .
I also reviewed two mathematical articles I have on the harmonica and both experiments controlled the volume of the resonating chamber in front of the harp. Changing the volume of this chamber, which was supplied with constant pressure air, would result in bends and overbends.
"Acoustical and physical dynamics of the diatonic harmonica"
Henry T. Bahnson and James F. Antaki
"Pitch Control in Harmonica Playing"
Robert B. Johnston
http://www.smithsonianmag.com/arts-culture/Scanning-a-Stradivarius.html#ixzz2ablp7dPe
Last Edited by STME58 on Jul 31, 2013 2:01 AM
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STME58
510 posts
Jul 31, 2013
1:25 AM
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I was able to aim a high speed camera at a harp tonight. I opened up the covers on a Special 20 with a Blue Moon Harmonica comb, clamped the harp in a fixed position relative to the camera and a bright light, and got a pretty good image. The amount of light I had allowed me to record at 3000 frames per second, about the minimum required to capture an Eb two hole draw at 311Hz. I had to open the lens aperture to get it to work, so I lost depth of field and the whole reed is not in focus. If I want to record faster I will need even more light. As it was, the reed was lit so brightly it was hard to look at. I had to close my eyes to play it as light came past the harp into my eyes and I did not have proper harmonica playing shades :).
This is looking up at the bottom reed. You can see the reed reduce amplitude as I bend the note. I have not yet counted the frames per oscillation to get the frequency it bent down to. I find it interesting that even though this is a draw, most of the time the reed does not enter the reed plate.I have other video where it does. I am not sure which mode is bent and which is unbent, counting frequency will help me sort that out. In the mean time here is a link to some video. I edited the file to shorten it but it is still 38M. 3000 frames per second produces a LOT of data. The video is 2 minutes long at 25 frames per second and shows one second of the reed vibrating.
Vibrating Reed
Last Edited by STME58 on Jul 31, 2013 1:53 AM
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mlefree
120 posts
Jul 31, 2013
9:56 AM
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Well, STME, ~that~ is one of the coolest things I've ever seen! It changed my thinking about how a reed vibrates relative to the reed plate. I had always imagined that the reed would travel much further into the slot than it apparently does. I had thought that the reed's travel through the reed plate would be more or less symmetrical with respect to the reed plate. It quite obviously "chops" the air flow by closing the slot off and then the reed raises again. I didn't see any dipping of the reed into the slot at all.
That was great, STME; keep it up!
Michelle
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STME58
512 posts
Jul 31, 2013
1:36 PM
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I was surprised to see the reed not going into the slot. One has to be careful about overgeneralizing from small data samples though. Because of the way this video was taken, I don't know what sound was occurring at the time. We also can not see what the blow reed is doing. Here is a sample of what I took yesterday showing 2 reeds vibrating at once and traveling much further.
Larger Excursions
Last Edited by STME58 on Jul 31, 2013 1:41 PM
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