Rudall - Rose, Prattens. Direct inj air column - embouchure

[an seanduine]

One of the images I have run across referring to the production of sound in a flute is that of a compressable spring oscillating. Picture a slinky inside the bore of the sounding chamber (this image covers stopped chambers like a bottle as well as open chambers like a flute bore.)
The far edge of the blow hole is not as important as the 'push-back' of the 'spring' in the sounding chamber in causing periodic redirection of the blowing out and away from the blow hole. This image readily allows for more or less direction of the injected blowing air into or across the blow-hole.
If you think of a bottle being sounded as a flute, the far edge has almost no 'edge' at all.
This image is similar to various analogies to the action of resonant cavities being injected with microwaves.

For what it is worth,
Bob

[johnkerr]

John, I understand the arguments and their history. But if your model is right, then the art of embouchure cutting is in getting the chimney right, not the edge. Changes in embouchure shape should be important if they change the chimney. Changes in edge shape shouldn't matter if they don't change the chimney shape. Do I understand you correctly?

Here's a thought experiment for you. If one blew through a small diameter straw (same diameter and shape as the opining in your lips) inserted just into the embouchure, so that the airstream couldn't hit the blowing edge, but wasn't inserted so far to significantly mess up the rebounding molecules, do you think you would hear anything? If I understand you, your model says yes, because air hitting the edge/chimney on the way in doesn't matter. Easy enough to do. If the experiment works this would save having to develop an embouchure, and make the flute like playing a whistle. I'll be rich, rich !!!! (evil laugh.....)

It seems to me that when I go up an octave, I am changing the direction of the airstream (less down), and when I go to the third octave I blow even less down (and with higher velocity). It's not obvious how this works if the edge/chimney isn't doing anything to the incoming air. I bet my straw blown flute wouldn't change octaves.

Keep in mind that I'm not describing the only way to get a sound out of the flute, I'm describing the best way to get the sound that Irish trad players strive for. When I change octaves, I don't change the direction of my airstream at all. I change the opening in my lips, which changes the cross-section area through which the stream comes out, which changes the pressure at which the air comes out, which either raises or lowers the pitch that's sounding by some interval - not necessarily an octave. By changing embouchure alone, with any given fingering I can sound the fundamental (e.g. xxx xxx = D), the first harmonic (D'), the second harmonic (A'), the third harmonic (D''), etc.

Re your straw hypothesis, if you could configure the straw to have the same cross-sectional shape as your (lip) embouchure opening and put out the airstream at the same pressure - and also cover up the same part of the flute embouchure hole as your lips inevitably do, then yes I think you would get a sound. But doing all that with a straw might not be possible.

[rogermace]

Now I can't even get a decent tone no matter how I try to blow my flute - front or back edge

below is a Physics site with some flute measurement/discussion points, but I would like to hear the results of any measurements that can be made here - they seem to ignore the back edge and maybe for bad reasoning:

http://www.phys.unsw.edu.au/jw/fluteaco ... l#together

and a quote:

'Lipping' up and down

The design of a flute involves compromises and many notes require slight pitch adjustment by the player. (See Tuning woodwinds.) Players lower the pitch mainly by a combination of drawing the chin back or pushing it forward, rolling the flute's embouchure hole towards them or away and changing the jet geometry. These actions do several things: (i) they increase the fraction of the embouchure hole that is covered by the lower lip, thereby decreasing the size of the hole opening to the atmosphere, (ii) they decrease the solid angle available into which the sound wave can radiate (informally: they 'get in the way of' the radiation), and (iii) they decrease the length and change the angle of the jet .


Effects (i) and (ii) increase the effective length of the flute and so make the resonant frequencies lower and the note flatter. Rolling the embouchure away and/or extending the lower jaw have the reverse effects, and so raise the pitch. Technically, these actions work because they change the radiation impedance at the embouchure: when a note is 'lipped down', the embouchure hole is "less open" (both the hole and angle are smaller so there is more impedance to radiation from the bore to the external field). The effects of the jet itself are more complicated.

We have measured these effects explicitly by installing our impedance measuring equipment in a flute head and measuring the impedance at the embouchure hole. (This is the impedance of the radiation field, 'looking out' from inside the blowhole, which is partially blocked by the lower lip. The flutist's lip and face also provide a baffle that reduces the angle for radiation. These results are reported in a recent conference paper - see our research papers site.) The interval that can be lipped depends on the details of the impedance spectrum and on some properties of the jet. It is easier to adjust the pitch of notes using a short length of tube, whose impedance spectra have fewer and shallower harmonic minima than do those of long tube fingerings. The analogous effects are much bigger on the shakuhachi, and are described on that site.

[Denny]

Players lower the pitch mainly by a combination of drawing the chin back or pushing it forward, rolling the flute's embouchure hole towards them or away and changing the jet geometry.

Is it not feasible to achieve both of those with manipulation of the lower lip muscles?

(check it out boyz and girrls....he is getting into bigger words!)

[treeshark]

Is it not feasible to achieve both of those with manipulation of the lower lip muscles?

That's the direction I am staggering in at the moment. I have for a while now been crushing my flute into my face
as per Mr Nicholsons instructions, and using my lower lip as an anvil for my top lip to push down upon.
But I've been playing other music that requires more dynamics recently and found that by lowering the flute on
my face a bit and rolling in less, I can get much more variety of tone and pitch because my lips can move around
more, it's a little harder but I think has brought some benefits for me at least. It's certainly less stressful and I might
still be able to play when my lower teeth drop out.

[Terry McGee]

Now, Holmes experiment shows us that, when blowing down into the embouchure, the angle which the air strikes the edge is much altered. But it still does strike the edge. It has to, or there could be no jet-vibrating air column interaction, which is the secret of the flute. The jet has to blow into the flute for positive wavefronts, and then out of it for the negative wavefronts. If it never makes it out, oscillation will cease.

Somewhere I've seen an image of the path it takes, made visible by inhaling smoke from a quite common tubular smouldering device no longer regarded as safe, but strangely, still legally available! The image is quite extraordinary - it's done using time lapse photography - so it's actually a series of images. The jet strikes the edge, then is deflected into the hole, then back to the edge, then way out into space, and so on. What is extraordinary is the degree by which the jet is deflected - more than its length! The image is probably on the web somewhere, but I haven't been successful finding it. Smarter searchers might! There's one involving organ pipes too, which of course is of interest to whistle players. In the whistle, the offset (the distance by which the jet is aimed away from the edge) is of course set by the maker, not the player.

Perhaps one of our more daring members who makes regular use of the previously-mentioned quite common devices and who has a video camera or a fast stills camera could carry out the experiment for us! If that player used the blow down into the centre of the flute approach, that would be specially great.

If you repeat Holmes' experiment with a larger blob of blue tack that reaches the edge, or some tape or something similar, you'll see that, even though you are blowing down into the hole, it stifles the tone. Holmes got away with it with his small blob because it would have been "over the horizon" from the direction the jet would be coming, after being directed down the hole. But with a player aiming at the edge, it would be right in the firing line.

Terry

[jemtheflute]

Just speculating here, but no-one has said this (clearly, at any rate) yet - could the difference between the two main embouchure techniques be this: that the French School "across" method involves splitting the air-stream at its lower edge, analogously with how a fipple-flute's labium/blade shaves the tiniest bit of the bottom of the duct-shaped air-stream, while the Nicholson/English school "down" method splits the upper or outer edge of the air-stream.....?

I'm of the opinion (based on my admittedly limited understanding of the physics - see the Hoots, Hertz, Harmonics articles here and the Ausi Uni woodwind website [can't find that link quickly, sorry]) that there MUST be some split of the air-stream to establish the requisite oscillation, as Terry says, but we know that in whistles, recorders etc. that split is nothing like in the centre of the depth of the air-stream, (which does not work at all well) but very near one edge of it. Holmes blob experiment is at least suggestive of a top/far edge split with the majority of the airstream entering the flute, whereas one would expect far more significant disruption to be caused by the blob if adopting a French School blowing technique. I don't think the mere turbulence of the airstream injected laterally into the tube (maybe affected by its passage over the angle at the change of planes between the embouchure chimney and the bore) without any contact against the outer rim is capable of proper tone-generation (though doubtless some resonance of the tube's sounding length will be agitated) - there has to be some airstream split against an edge of some kind, even a crude, blunt one like the edge of a bottle's neck.

Re: the condensation "shadow" on the outer side of the flute tube/embouchure plate - even in French School embouchure technique, that narrow V, narrower than the embouchure hole, is desirable, indicative of a good embouchure with a well-directed and laterally narrow (so not wasteful) airstream - and has little to do with how much of the air-stream goes which way in vertical terms.

[Holmes]

That's all very interesting, may I add an experience that I have not heard anyone express before? When I get my tone focused, I have the near edge not covered by any lip whatsoever, get my top lip over and as close as physics will allow and of course the near edge into the air column. I can feel the predominant sound production move down the flute, away from the embouchure and it appears to move into the body of the flute & everything is enhanced (tone, projection etc). I'm willing to accept this as an "out of body experience" (ouch). however I can repeat it but I can't say if it's actual or imagined. I've talked to some very good blowers about this but they usually make their excuses and politely leave! (I don't use drugs)

Regards

H

[hans]

So what happens when you put the bluetack blob right onto the far edge, obliterating the "edge" and creating a wall there? This should cover at least half of the circumference.

[Holmes]

So what happens when you put the bluetack blob right onto the far edge, obliterating the "edge" and creating a wall there? This should cover at least half of the circumference.

The blutac was on the edge when I was playing, photo for illustrative purposes, it fell off, I stuck it back on to photograph but I was a mm or so out for the photo. - I have never tried to claim that the furthermost edge has no influence, just not that traditionally associated with it for certain players. There are makers that make a feature of the furthermost edge, embellishing or ornamenting giving the impression that this is the playing edge. For me, it's not as important as all of the things I've repeatedly mentioned. I don't have a problem with makers that embellish the aforementioned, I'm just making a point.

Regards

H

[Kirk B]

I think it's time to call in the big guns. They have all those expensive toys like FLIR imaging systems.

[Denny]

I can not get these to come up on this PC
I think that they are pertinent to the discussion.

http://www.phys.unsw.edu.au/music/flute/
http://www.phys.unsw.edu.au/jw/fluteaco ... tml#airjet

[rogermace]

I had referenced this site earlier since it discusses flute acoustics in much detail. But as you can see from this page, they do not consider blowing the stream into the back of the flute's embouchure - especially since the back of the embouchure is usually not machined to accurately split an airstream. See diagram they used in the article:

http://www.phys.unsw.edu.au/jw/fluteaco ... ml#lipping

[Rob Sharer]

Chris Wilkes is another who advocates blowing straight down, as if you're trying to blow a grain of rice off of your chin. Of course, he's also someone who makes very traditional copies of Rudall-style flutes with original-style, small, vertical embouchute cuts...



Coincidence? You decide.


Rob

[treeshark]

Chris plays with amazingly little air, but he doesn't seem turn the flute in much.
He just hits the blowing edge with a very accurate tightly focused jet of air, he can do the
same thing with the head rolled quite far out which I found interesting.
He also told me not too blow too hard. I think he's the best blower of the flute
I've ever had the chance to observe close too, he can play way up in the 3rd octave with no apparent strain,
but seeing it done and emulating it are very different things.