 The Clarinet BBoard
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Author: Sal
Date: 2001-02-18 14:04
Can anyone tell me how we manage to 'choose' which harmonic to play? In other words, what are we doing differently when we play a leger-line E to when we play a leger-line A above it?
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Author: Dee
Date: 2001-02-18 14:44
Embouchure control
Breath control
"Thinking" the right pitch
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Author: Anji
Date: 2001-02-19 01:02
I think the reed beats only at it's resonant frequency in the air column set up in the horn (a tuned circuit aka 'Tank circuit' to use an electrical analogue).
As players, I think we have a remarkable, but limited range of modification we can make to the fundamental. Most of these are amplitude and intensity modifications, at the reed.
Most of the tuning in a stopped pipe is done at the fulcrum of the spring (where the reed is attached by the ligature). The rest of the selection is made by matching the exit ports to the frequency we seek to release (tonehole placement).
The over and under tones are much smaller in amplitude than the fundamental, so actually getting one to pop out requires extreme modification of the motion at the fulcrum, by dampening the fundamental.
Then again, telepathy may be the actual answer.
The simplest explanation that encompasses the most facts is usually the correct explanation.
anji
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Author: Mark Charette
Date: 2001-02-19 02:01
Anji wrote:
> I think the reed beats only at it's resonant frequency in
> the air column set up in the horn (a tuned circuit aka 'Tank
> circuit' to use an electrical analogue).
Totally wrong. The reed vibrates in multiple modes, both laterally and longitudinally. Movies of the reed oscillations have been made; it is not a simple vibration by any means. There have been a number of presentions made at Clarinetfests. Two that I attended that had relevance:
Reed Science: A Summary of Current Empirical and Theoretical Progress - Donald Casadonte
A New Material for Woodwind Reeds - Guy Légère
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Author: Anji
Date: 2001-02-19 12:50
I obviously need to see the Casadonte and Legere papers. I haven't read them so I can't address there research.
If we did a frequency sweep analysis, would we find the reed beating at a different fundamental frequency in all registers/notes?
How large is integral described by the contibution of these harmonics, when compared to the fundamental frequency?
I did some tuning of a traditional organ and found that debris in the pipe and throat contributed as much, if not more than the condition of the reed spring at the aperture. (This is a fairly close approximation to the clarinet, a stopped pipe.)
I remember a demonstration with a tenor sax (different bore geometry, so it may be apples to tangerines as a comparison) where the transducer on the reed read the same frequency throughout the demonstration. A pipe of compressed air was released at a constant pressure (flow changed dramatically in the demo) across the reed with a piece of Tygon tubing as the linkage.
The notes popped right out (sounded terrible, but it worked).
Here's the point, the reed beat at the same fundamental (somewhere around 1 kHz) through out. No spectral analysis of harmonics was done.
What I'm getting at is this, if we had to select the bell mode of each note at the reed wouldn't the horn be impossibly difficult? Since we accentuate the fundamental and the fundamental reflects within the column, aren't we just tuning the resonant chamber so that the airway coincides with the port that is open?
Don't the harmonics contribute to the richness or harshness of the sound?
I'm also trying to get a handle on what "dark" or "bright" means in the clarinet context, so my query is clearly at a novice level.
anji
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Author: Mark Charette
Date: 2001-02-19 13:08
Anji,
The only way to settle any of your questions or of any other is to read the papers or do the experiments. The harmonics of course contribute (or actually create) the timbre.
There's been work on "dark" & "bright" sounds - have you read any of Benade's work? He clamed (and did experiments to prove) that our general perception of "dark" and "bright" had much to do with cutoff frequencies.
You really should start reading the acoustic textbooks.
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Author: Anji
Date: 2001-02-19 16:54
Quite right, I'm fumbling around in the (Hem) dark trying to sort this out.
Are there references in the Sneezy archives?
The only details I have so far read are clearly simplified descriptions of the air column and venting. The reed is treated as a pure oscillator (it clearly isn't, anyone who has played can feel lotsa stuff happenin') for the sake of modelling.
We did some dynamic load testing of a bridge with a 9G oscillator and found some amazing modes that are invisible to the eye, but could be felt.
I just hope I don't end up like the centipede trying to remember which foot comes first.
anji
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Author: Mark Charette
Date: 2001-02-19 23:43
Anji, the reference book I use most is Art Benade's "Fundamentals of Musical Acoustics". Easily comprehended by most anyone with a high school math education.
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Author: Anji
Date: 2001-02-20 00:34
Hey MC,
(Sal, sorry if you're bored silly by this thread, by now.)
<Easily comprehended by most anyone with a high school math ed.>
That would be me. Too many "Sleep signs" in the last text I thumbed through.
Did wonders for insomnia, anyway. Inegrate the area und....Zzz.
I just did an archive search and found Abe Galper's treatise, now I know where the school got it's idea for the sax experiment... his paper describes nearly the same rig.
Jonathan Cohler's stuff is informative too, especially about multiphonics.
To paraphrase Galper, "The fundamental freq. of the reed vibration...is the same in all ranges to within one percent as the fundamental frequency of the tone produced."
"This might appear surprising since harmonic analysis shows that the energy associated with the fundamental is practically negligible for all loud tones."
So, louder passages employ more harmonic + inharmonic overtones?
(I think I'm getting the spectral picture here, and an explanation of tone color, all in the same lunchbox.)
Also from Ave, "For a tone of good quality the tip of the reed VIBRATES AS A UNIT (my emphasis, Ave doesn't shout) e.g. it remains parallel to the facing of the mouthpiece. Tones of poor qualities are associated with variations from the normal mode, and they may be encountered under a variety of playing conditions...
Good quality seems to be associated with symmetry both as regards embouchure pressure and reed design."
What I'm getting at is reed balancing and a steady embouchure, sans gnawing, are the goal my teacher goads me toward. These produce a predominant fundamental (that shifts with each note?) and minimizes other oscillations.
Being cognizant of multiphonics and other hash may not be helpful in the development of a stable tone, insomuch as a properly balanced reed on a symetric mouthpiece with a constant embouchure minimizes these additional overtones.. until you play loud, anyway.
Am I narrowing in on this?
anji
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Author: Mark Charette
Date: 2001-02-20 01:55
Abe was wrong as regards the reed vibrating as a unit - the movies showed the reed moving in different modes. Unequivocally. I'll bet Abe did his experiments a while back (Abe's a buddy of mine; perhaps I'll give him a call this weekend). What was the exact reference (Web page)?
Higher frequencies contain more energy. There aren't any tones other than harmonic (integer multiples) of the fundamental and possible pink (shaped) noise. I did some spectral analysis with Jim Pyne of clarinet tones and thought I saw some inharmonicity (which should be impossible), but further observation of the data showed I was wrong.
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Author: Rene
Date: 2001-02-20 05:34
It would be most surprising, if the reeds vibrates as a unit. Seems difficult to observe though.
The vocal cords of singers have been recorded using flash lights (or fast speed cameras, don't know), and they show a movement of the opening from one end to the other, and reappearing at the one end. This seems a more economical movement.
I'd expect a similar movement of the reed top starting in the middle and and ending at both sides, or the other way around.
Anyway he reed must vibrate with the basic frequency. A little bit of arithmetic (or book reading tells us the clarinet contains a quarter length air wave. Thus it is most likely to go from a pressure node (most pressure change) to a no pressure node (no pressure change). The former in the mouthpiece, the latter at the tone hole. The pressure changes open and close the reed, and the air support from the mouth feeds the wave.
This all looks obvious. However, I would love to do exact measurements of this.
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Author: Gordon (NZ)
Date: 2001-02-20 11:15
KISS approach: I reckon to get a higher harmonic (with same fingering) I put the pressure very slightly further down the reed, and probably use a little more teeth pressure which transfers through the lip and localises the pressure more to the centre and less at the sides of the reed. Incidentally if one has an extra hard reed that makes some notes go fuzzy sounding (possibly from inadequate tone hole venting), this application of more pressure at the centre of the reed seems to clear the notes somewhat.
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