Mujitsu and Tairaku's Shakuhachi BBQ

Toby · 2009-12-25 20:03:06

Just to get a breath of fresh air, I have started a new thread.

I ran across this in Nederveen's book, and I think it helps explain how very small geometric changes in the bore can affect the sound in ways that intuitively seem impossible:

"Ease of blowing, "resistance", "feel" or whatever name the musician attaches to his feelings of comfort in blowing his instrument are presumably related to the correct matching of the acoustical impedances of generator and tube. The strong partial content which is inherent in reed and hole excitation requires this condition to be fulfilled not only for the fundamental component of the playing frequency but also for the frequencies of its overtones. It means that the tube itself must have a harmonic set of overtones. The frequencies of these overtones are sensitive to minor changes in the bore, to hole lengths and to tube segments between holes in that part of the tube where all holes are open. The oboe and the bassoon especially are known for their particular sensitivity to changes in hole arrangements. There are notes which become unstable and difficult to blow steadily when (open) hole positions on the lower tube piece are modified.

A subject of repeated discussion is the influence of wall vibrations on the tone quality. Most musicians claim that the wall material is important; with a few exceptions, scientists deny this. Let us consider the facts. First of all, it is quite certain that the walls vibrate. This can be felt with the fingertips and it has also been measured. But the contribution of wall vibrations to the harmonic composition of the total of radiated sound is very small: it has been measured as well as calculated that the sound power radiated by the walls is about 40 dB (10000 times) below that given out from the holes. Investigations on the steady-state partial composition of woodwinds made from various materials have revealed that only in rare cases (e.g. thin-walled tubes of non-circular cross section) are the wall materials found to influence the composition of the partials. It seems that other opinions on this matter, as reported by some authors, are based on questionable or no evidence at all. These investigators apparently did not take all possible precautions by ruling out any slight differences in geometry when they compared instruments of different material. This leads us to some reflections on minor geometrical fluctuations.

A minor geometrical change can have a large influence on the composition of the partials of a blown tube and hence on the tone quality. This can be understood when we realize that the excitation mechanism oscillating in steady state produces a set of partials which constitute a harmonic series (exact integer multiples of the fundamental frequency). If due to some small change in the bore, the resonance frequency of a partial changes in an amount comparable to the width of its resonance curve, we may expect a considerable change in the amplitude of this partial; a similar effect would appear had the partial been excited by some external source, first in resonance and then, after a slight frequency shift in the source, out of resonance. Slight changes in the bore may thus enhance some partials and suppress others, leading to changes in the timbre of the instrument."

Toby

Toby · 2009-12-25 23:28:41

Small geometric changes across the bore have more effect across the range of the flute. Spot changes have effects only on notes which have a node or antinode of the fundamental frequency or one of its harmonics on the spot where the change was made. This means that a spot change can have a strong effect on some notes and no effect on others, with smaller changes happening for the others.

You may have heard of "W curves". These are charts of the nodes and antinodes for various notes (they change with each note). If you know where these are for any given note, you can figure out (more or less) what effect spot changes will have on that note at any position along the bore. If you superimpose the change on the W curves of other notes, you can then also see what effect that spot change will have on other notes. It can get pretty complicated--one acoustician described is as akin to playing three dimensional chess--but it ain't bad to have an idea what will happen before you start with the garibo or the ji paste...

We are lucky not to have so many notes on the shakuhachi: that means that an experienced maker can probably "feel" his way along, having probably experienced similar tuning and response problems many times and knowing what he did to fix them in the past. But for the rest of us having some idea where to start is not bad.

Toby

Last edited by Toby (2009-12-25 23:30:25)

Toby · 2009-12-25 23:33:23

Here is a nice and clear summary of the materials debate:

http://www.bretpimentel.com/does-materi … -to-agree/

Worth a look. No math.

Toby

rpowers · 2009-12-26 00:59:56

Jon wrote:
So, small geometric changes to the entire length of the bore or "spot tuning"?

I'm afraid the response to this question is, "Yes."

radi0gnome · 2009-12-26 08:48:43

Toby wrote:
Here is a nice and clear summary of the materials debate:

http://www.bretpimentel.com/does-materi … -to-agree/

Worth a look. No math.

Toby

Great no math, now I don't have to worry about statistical significance on a paltry sample of 27 test subjects. Tossing that aside, the next argument I think a flute player who believes material makes a difference would come up with is that Dr. Coltman used a plastic for the head joint. Most what I've heard among flute players regarding material is that the head joint was the most important. Eg., If you don't want to shell out the bucks for a silver flute for your kid, get nickel-silver with a silver head joint, or if you are a poor but advanced student who can't afford a gold flute, get a nice gold head joint for that silver Powell you're playing. That's because the head joint makes the most difference anyway. At least that's what I remember hearing from when I used to hang out with those people.

As far as shakuhachi are concerned, I remember reading something about cracked and repaired flutes supposedly sounding better. I'm thinking that splinters could maybe be vibrating in a similar manner that the article says a loose clarinet key would. I know the resultant vibration wasn't supposed to be the right frequency and the article says wouldn't be a pleasant sound, but that is really a matter of taste. I know of one musical instrument where the players like that sort of thing, on a lot of styles of African thumb piano they like to put metal peices on the keys that buzz at what seems to be arbitrary frequencies, and that's consudered a good thing. A lot of the non-"silver flute"-like tones that are considered good on shakuhachi would probably be considered unpleasant to silver flute players except in modern music, maybe a hint of atonal buzz is cool thing for shakuhachi.

edosan · 2009-12-26 14:44:51

Jon wrote:
Hey Toby,

Thanks for the info. Is this the same as the stuff on Navaching.com? I wasn't able to come up with much from google searches using the key words "W curves" "nodes" "antinodes" etc. in various combinations.

Perhaps this will help. It's from a discussion of how to optimize room acoustics a sound studio. It takes off from the definition of 'Standing Wave', then brings in the nodes and antinodes in describing portions of sound waves. If you consider W Curves in the light of the excerpt below, the idea behind them may become clearer: a method of charting the patterns of nodes and antinodes for a given note.

"What is a standing wave?

A particular pattern of constructive and destructive interference** is called a standing wave, which is essential to the way string instruments produce sound, but very undesirable in the listening environment of an electronic studio.

The characteristic mode of vibration of a string with one fixed end is the standing wave pattern. In a normal reflection of a sound wave from a hard surface, the phase of the reflected wave is not changed. With a wave induced in a string with a fixed end, the wave reflects from the fixed end out of phase with the incident wave, creating patterns of constructive interference at certain resonant frequencies. Nodes and antinodes on the resultant string correspond the points of minimum (node) and maximum (antinode) vibrations. Air columns in both closed and open tubes also exhibit standing wave properties. In this case, the nodes and antinodes refer to the minimum (node) and maximum (antinode) pressure in the tube. Woodwind instruments are examples of half- or quarter wave resonators that produce multiple standing waves—the differences are whether the tube is open at both ends (flute, including the embouchure hole) or closed at one end, such as the oboe or clarinet."

**When sound waves are propogated within a space, they not only collide with the surfaces of the space, they run into each other, creating 'patterns of constructive and destructive interference'.

Here's the link this was excerpted from: http://www.indiana.edu/~emusic/acoustics/reverb.htm, which is a discussion of room acoustics.

Last edited by edosan (2009-12-26 14:54:54)

Toby · 2009-12-27 08:24:04

Hi Jon,

If you google "w curves" woodwind you will get a link to a google book result for Benade's "Fundamentals of Musical Acoustics"--unfortunately some pages are not shown. Alternately go to:

https://ccrma.stanford.edu/marl/Benade/

Writings >70s and under 1977 you can download a pdf called "Acoustic evolution of wind instruments". He starts talking about adjusting bores with perturbation w curves on pg. 39, but I warn you, you might find this much more WTF than that quote I posted at the top of the thread.

Toby

radi0gnome · 2009-12-27 08:55:56

Toby, do have any solid acoustical information about throat tuning? It is a practice where the flute player pretends to sing the same note as he's playing to shape the throat. The theory is supposed to be something like the mouth and throat are part of the acoustic system and if you tune them to resonate with the note you are playing, it will sound better. Robert Dick goes so far to say that if you've ever produced a beautiful tone you've used throat tuning, even if you didn't realize it, suggesting it is a requirement for a beautiful tone.

I've got to admit I'm a bit skeptical because intuitively for me it seems like the difference in tone due to anything past that tiny hole the air is coming out of will likely be too small to perceive, particularly when the surface of the tube past that point is soft biological matter. However, the practice seems to work for some reason. And I know Robert Dick has worked closely with doctors and acousticians when researching many of his teaching techniques.

Toby · 2009-12-28 05:37:31

radi0gnome wrote:
Toby, do have any solid acoustical information about throat tuning? It is a practice where the flute player pretends to sing the same note as he's playing to shape the throat. The theory is supposed to be something like the mouth and throat are part of the acoustic system and if you tune them to resonate with the note you are playing, it will sound better. Robert Dick goes so far to say that if you've ever produced a beautiful tone you've used throat tuning, even if you didn't realize it, suggesting it is a requirement for a beautiful tone.

I've got to admit I'm a bit skeptical because intuitively for me it seems like the difference in tone due to anything past that tiny hole the air is coming out of will likely be too small to perceive, particularly when the surface of the tube past that point is soft biological matter. However, the practice seems to work for some reason. And I know Robert Dick has worked closely with doctors and acousticians when researching many of his teaching techniques.

Actually, there is some evidence that the oral cavity acts as an upstream resonator in some cases, although nowhere near to the extent that it does in a clarinet or sax, for example, where there is direct coupling between the air reservoir and the air column. The effect is not large, but it definitely has more of an effect that the material of the walls on the final sound. That being said, probably most of the effects that musicians perceive have more to do with not with the throat, but subtle changes in the embouchure and air stream when they change their throat configuration.

The criticism that you have of the Coltman experiment has been advanced before, but it is not really valid for a couple of reasons. First of all, the heads of Coltman's flutes were very short: just the embouchure hole and a bit more. Second, there is no reason to think that the material of the head joint is any more important to the sound than any other part of the flute. Flautists find head joints significant because of the fact that small changes in the geometry of the embouchure hole and tube (which is not cylindrical near the hole) affect the sound quite a bit more than different flute bodies, which are all cylindrical and basically the same.

Finally, and most importantly, all Coltman's test subjects did feel that there was a significant different between the three flutes when they could see them; the difference only disappeared in the dark.

Toby

Last edited by Toby (2009-12-28 05:39:21)

Mujitsu and Tairaku's Shakuhachi BBQ

#1 2009-12-25 20:03:06

more on acoustics

#2 2009-12-25 23:28:41

Re: more on acoustics

#3 2009-12-25 23:33:23

Re: more on acoustics

#4 2009-12-26 00:59:56

Re: more on acoustics

Jon wrote:

#5 2009-12-26 08:48:43

Re: more on acoustics

Toby wrote:

#6 2009-12-26 14:44:51

Re: more on acoustics

Jon wrote:

#7 2009-12-27 08:24:04

Re: more on acoustics

#8 2009-12-27 08:55:56

Re: more on acoustics

#9 2009-12-28 05:37:31

Re: more on acoustics

radi0gnome wrote:

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