physics -why doesn't a Beohm flute need a lot of breath?

[ertwert]

Hi,
If you compare bore and tone hole sizes of conical flutes, you notice, that flutes with a bigger bore and tone holes need more breath.
Why is Boehm flute, that has such a big bore, so easy to play?

[cac]

Your question is interesting, and I hope there is a physicist among us who can answer it (or someone with a better memory than I have who can refer to published work by flutist physicists). I can say, with considerable diffidence, and based on my experience as a player, that I'm not even sure that bore type makes much of a difference at all. I think embouchure and tone hole sizes are probably more important. I have four types of conical bore flutes: baroque flutes (with very small embouchure hole and tone hole size), Rudall & Rose type flutes with elliptical embouchures and small tone hole size, an Olwell "Nicholson" model with an elliptical embouchure and medium size tone holes and a "Pratten" model flute with a somewhat larger embouchure which I would describe as two semicircles at the sides with some straight lines connecting the two semicircles and large tone holes. I have silver flutes with very large tone holes and large embouchures (rectangular with rounded corners). The amount of air these flutes require goes from very little to quite a bit. I don't notice much difference between the air required for the Pratten-type conical bore flute and the silver Boehm type flute. All the others take less air. Do you feel that the Boehm flute takes less air than a large-holed conical bore flute when playing the same type of music? Note that I've assumed, given your first sentence, that by 'easy to play' you mean require less air. There are other dimensions to ease of playing that may also be relevant. It is said that the typical embouchure hole of the Boehm flute (rectangular with rounded corners), as preferred by Boehm himself, is easier to play. This hasn't been my own experience, however. And certainly the Boehm system of axles, clutches and the like makes it easier to play in keys with many flats or sharps, assuming the conical bore flute has a 'simple' system key arrangement.

[piperjoe]

Is it possible that we're not "filling" the flute, but rather, making the air that's already in there vibrate.

That's how I think it was explained to me back when I was a music major. But I didn't pay a lot of attention to my teachers in those days so I could be remembering it all wrong.

While my alto flute does take more air than my C flute, both Di Zhaos by the way, it has a larger embouchure so I think my theory holds up. But I'm sure that Jem or Casey or someone really smart like that will set us/me straight.

Piper Joe

[Terry McGee]

Hi,
If you compare bore and tone hole sizes of conical flutes, you notice, that flutes with a bigger bore and tone holes need more breath.
Why is Boehm flute, that has such a big bore, so easy to play?

It's a good question. See if this seems to be heading towards a good answer.

It's the flow of our breath into a flute that provides the energy to excite the air column and produce sound. So if a Boehm flute is easy to play, it's because it is more efficient - i.e. it can make more sound from a given amount of air flow. So the question becomes, why is a Boehm flute more efficient than our conical flutes?

I can think of a few factors:

- the ideal bore diameter of a flute varies with the pitch of the note being played. Think of a fistful of whistles*, from the tiny sopranino F to to massive low D. Our conical flutes vary from 19 to about 10.5mm. Counter-intuitively, the bore at the low end is the narrowest, not the widest. A Boehm flute varies between 17 and 19mm, with the widest end towards the lowest note.

- any restrictions of venting area at the keyholes reduce efficiency. The area of the holes is high in the Boehm flute.

- Venting support. In our flutes, the next open hole below the last closed hole is typically a tone away (except between R1 and R2, a semitone separation which helps G to be a strong note). In the Boehm flute, it's always a semitone.

- big, open embouchure holes with a lot of "edge" helps convert more airflow to sound.

Now, I don't accept for a moment that condemns us to playing wuzzy, weak flutes. Indeed, I remember when I first went to meet the woodwind acoustics chappies at Physics UNSW, they were stunned (and maybe appalled?) at how loud my conical flute was. But it does require us to use different embouchure techniques to our Boehm flute cousins. I think chief among these is higher jet speed, narrower jet dimensions and jet offset.

Higher jet speed would make the flute very heavy going unless coupled with narrower jet dimensions. This equates to higher pressure in the mouth, tighter embouchure and less flow than the typical Boehm flute player uses. The late Prof Neville Fletcher and I did measurements that showed this was the case. (It can also equate to noisy, hissy sound if not well focused.)

Jet offset means we don't blow at the far edge of the hole, but more towards the bottom of the far edge of the hole. This offset puts more of the energy into the second (and subsequent) harmonics, giving more apparent power and cutting edge. I try to talk about this here: http://www.mcgee-flutes.com/Getting_the ... k_tone.htm . You might find this helpful if you need to change your approach to suit our flutes better.

But note this. Any leakage in a flute whatsoever really screws with the efficiency. So make sure your flute is totally (and I mean totally) airtight before trying other approaches. And check stopper spacing.

*I'm remembering the colourful Scots expression, the kist o'whistles. A kist is a chest in Scots. A "kist o'whistles" is a pipe organ, regarded scathingly by some Protestant sects as an unwanted diversion in Kirk.

[cac]

Terry, I was hoping you might contribute to this thread, although you haven't in the way that I had hoped (I'd hoped you'd have some way of measuring the amount of air going into the flute to produce a sound at a given note). But to comment on your suggestions, some of them seem to suggest less air is being used in the conical-bore flute: (1) the tighter embouchure of the conical flute means less air is used, (2) the "big, open embouchure" of the Boehm flute means more air is being used. Another point I think is indifferent to the issue: 'we don't blow at the far edge of the hole but more towards the bottom of the far edge of the hole.' -- the idea, taught in a number of classical flute manuals and the like, that the flutist aims at the far edge of the mouth hole, has been debunked for a long time. Back in 1968 I was taught by a student of the great Swiss flutist Aurele Nicolet to blow down into the flute, not across it, and there is at least one video on YouTube of James Galway discussing the embouchure where he says exactly the same thing. I believe William Bennett also teaches this. Other points I don't understand: how can the greater cross-sectional area of the Boehm flute contribute efficiency? I would think it would take more energy to excite the greater mass of air. Finally, some of your points make good sense: (1) hole size, (2) venting support. So I think that the claim of the original poster, viz. that the Boehm flute doesn't need a lot of breath, needs to be demonstrated. Do you know of anyone who has investigated the matter, or have equipment you could use to investigate it yourself? The only additional point I can think of to add right now is that much more of the time spent playing a Boehm flute is spent in the second and third octaves than in Irish music, and that might contribute to the notion that the Boehm flute requires less air. And let me apologize in advance if I've misunderstood some of your points (due to my own stupidity, not your lack of clarity-- I'm not very good at understanding mechanical/physical matters). Chet Creider

[paddler]

I have a few thoughts on this. First, I'm not convinced that cylindrical bore Boehm flutes take less breath than conical bore Irish flutes. My limited personal experience tends to suggest the opposite, if anything. Nevertheless, I agree that Boehm flutes are pretty easy to play even though they have a much larger body bore size. I think the ease of play comes from the following factors: (1) embouchure cut, which is typically larger and with a wider target zone on the splitting edge. Some Irish flute makers employ similar embouchure cuts to make their flutes easier to play. (2) full metal head and body, meaning that the entire bore surface is efficient in terms of energy losses, (3) excellent venting on all notes, meaning that it doesn't have notes that are especially difficult to sound well, such as the E note on our Irish flutes which generally has very poor venting and hence has a veiled sound.

I also wonder if the diameter of the head bore contributes anything to ease of play. We tend to talk about the bore of the Boehm flute as being much larger than our Irish flutes, but the diameter of the head bore at the embouchure is actually a lot smaller on a Boehm flute than on an Irish flute. I understand why it is this way, but I'm yet to be convinced that this makes the flute easier to play.

[Terry McGee]

(I'd hoped you'd have some way of measuring the amount of air going into the flute to produce a sound at a given note).

It's not easy to measure the amount of air going into the flute by any normal physical means, as we can't just interpolate a flow meter. (You can with the whistle.) But you can do quite meaningful comparisons by simply taking a full lungful of air and seeing how long you can blow a note for. Ideally, you'd want to blow the same volume of sound on both instruments, which you could monitor using a VU-meter app for the PC or phone. Do a few runs and average the results to increase precision.

You can measure breath-pressure while playing using simple made-at-home equipment. To capture the pressure hold a short length of capillary tubing in the corner of your mouth. It connects to the inlet of a manometer, which could either be a commercial meter (if you can get one in a sensitive-enough range, you're unlikely to impress your car-tyre gauge much!) or a simple U-tube manometer made from wood and thin poly poly pipe. Google "U-tube manometer images".

[ChrisCracknell]

As a player of both Boehm and Simple system, I have to say that I do not find that the Boehm flute is easier to play in the sense of requiring less effort. The Boehm Embouchure is usually cut more forgivingly, making it easier to get _some_ sound out of the flute, but filling either flute seems to take about the same effort, although they do need different blowing. But every flute that I have tried has needed adjustments of the air stream size, speed and direction to get the best out of it.

Often people play the conical simple system at full volume the whole time - makes sense in a loud session situation - whereas the Boehm flute is usually played in situations where most of the time is spent in the middle or quieter dynamic ranges.

And one also needs to be aware that loudness and projection are two different things. Whatever one may think of James Galway's Irish flute playing, I was still able to hear him playing pianissimo over an orchestra from the gods of the Laeiszhalle (formerly "Musikhalle", then Hamburg's main classical venue until the new Elbphilharmonie was built at huge cost to the Hamburg taypayers...)) . That is probably 30 meters away and at least ten higher. Achieving good projection on either flute is, for me, about the same effort whatever the volume.

Why might it seem like less effort on a Boehm? If the embouchure is being tightened with extreme effort from the lips then that can lead to muscle fatigue in the face which might lead to a perception of effort, but a tight embouchure can and should be achieved without needing to cramp up the lips. And a Boehm flute will often be played with a more relaxed embouchure anyway since that is frequently preached by classical teachers. Just a theory...

Anyway, YMMV.

[cac]

Here are a few time comparisions, following Terry's suggestion. I held each note as long as possible. The flutes were a Haynes solid silver flute and a Rob Forbes 'Pratten-type' delrin flute (I didn't have a wooden Pratten style flute at hand as my wooden flutes are medium- or small-holed and require much less air than these two). Times are in seconds, timed by me using the second hand of my wristwatch.

Note Boehm Conical
G 15 18
D 14 15
D' 22 27
G' 25 30

Although the conical flute seems to take a bit less air, the differences are slight and I don't notice a difference when playing them. Chet

[waltsweet]

A critical parameter is the bore diameter at the flow stations (the "displacement antinodes"); in other words, at the blowhole, and half a wavelength down the bore. On a trad flute, once you get away from the lowest notes, these two stations are rather large, but on a Boehmflute, you always have one station rooted in a small bore (17mm = 0.669") at the blowhole. This effect is especially noticeable in the 2nd and 3rd octaves. Also, the Boehmflute is well-designed to support the harmonics, so the player doesn't have to work as hard.

My new fife model is "CONSTITUTION" with a Boehm-style bore. Characteristically, the high notes are easy. If the high notes are much easier, then the instrument can be designed with a bigger bore overall, and this feature will enhance the low notes (without making the high notes too hard).

[oleorezinator]

As a player of both Boehm and Simple system, I have to say that I do not find that the Boehm flute is easier to play in the sense of requiring less effort. The Boehm Embouchure is usually cut more forgivingly, making it easier to get _some_ sound out of the flute, but filling either flute seems to take about the same effort, although they do need different blowing. But every flute that I have tried has needed adjustments of the air stream size, speed and direction to get the best out of it.

And one also needs to be aware that loudness and projection are two different things. Whatever one may think of James Galway's Irish flute playing, I was still able to hear him playing pianissimo over an orchestra from the gods of the Laeiszhalle (formerly "Musikhalle", then Hamburg's main classical venue until the new Elbphilharmonie was built at huge cost to the Hamburg taypayers...)) . That is probably 30 meters away and at least ten higher. Achieving good projection on either flute is, for me, about the same effort whatever the volume.

Why might it seem like less effort on a Boehm? If the embouchure is being tightened with extreme effort from the lips then that can lead to muscle fatigue in the face which might lead to a perception of effort, but a tight embouchure can and should be achieved without needing to cramp up the lips. And a Boehm flute will often be played with a more relaxed embouchure anyway since that is frequently preached by classical teachers. Just a theory...

Speaking of Galway and embouchure...
https://youtu.be/VQg0vScnQ8E

[waltsweet]

The trad flute, with tapered bore, gives rise to more harmonics. This type blends better, but doesn't cut thru as well as the other.

[PB+J]

I find the boehm flute easier to play, putting aside the more complex fingering opportunities. I think it’s because it’s more uniform in response-as paddler said, the different sized tone holes produce different timbres and volumes and when I started out on the Irish flute the Eb, for example drove me nuts. Now I’ve either gotten used to it or learned to compensate or both. The genius of the boehm flute is the predictability of the timbre from note to note. You aren’t constantly having to blow harder or softer just to maintain a relatively uniform volume. I much prefer the six hole flute and I’m not sure why. Partly the feel of the air column I think