Physics for flute owners

[MarcusR]

Ever wondered what the resonances down the flute bore looks like when you play your favorite reel or jig?

Here is a little home experiment you can do during the holidays,
all you need is a Hall crystal flute and some propane

The Rubens Tube Standing Waves:
http://www.youtube.com/watch?v=HpovwbPGEoo

Cheers!

Have a nice Christmas and a Happy New Year!

/MarcusR

[Jon C.]

Ever wondered what the resonances down the flute bore looks like when you play your favorite reel or jig?

Here is a little home experiment you can do during the holidays,
all you need is a Hall crystal flute and some propane

The Rubens Tube Standing Waves:
http://www.youtube.com/watch?v=HpovwbPGEoo

Cheers!

Have a nice Christmas and a Happy New Year!

/MarcusR

Apartment dwellers probably should not experiment with this!
It really illustrates where the nodes and anti nodes form when a tone is played on a flute. This is important when designing a flute, as if there is a perturbations in the bore where the node is touching, it can dampen the tone. Notice when a complex tone was generated, how many different nod locations there would be. Luckily they already worked the flute design out in the 19th century. It would be interesting to right a program, that would show the different notes vibrating in a conical tube, to see how they are effected by the contour.

[daiv]

Ever wondered what the resonances down the flute bore looks like when you play your favorite reel or jig?

Here is a little home experiment you can do during the holidays,
all you need is a Hall crystal flute and some propane

The Rubens Tube Standing Waves:
http://www.youtube.com/watch?v=HpovwbPGEoo

Cheers!

Have a nice Christmas and a Happy New Year!

/MarcusR

Apartment dwellers probably should not experiment with this!
It really illustrates where the nodes and anti nodes form when a tone is played on a flute. This is important when designing a flute, as if there is a perturbations in the bore where the node is touching, it can dampen the tone. Notice when a complex tone was generated, how many different nod locations there would be. Luckily they already worked the flute design out in the 19th century. It would be interesting to right a program, that would show the different notes vibrating in a conical tube, to see how they are effected by the contour.

what's a node?

[daiv]

Ever wondered what the resonances down the flute bore looks like when you play your favorite reel or jig?

Here is a little home experiment you can do during the holidays,
all you need is a Hall crystal flute and some propane

The Rubens Tube Standing Waves:
http://www.youtube.com/watch?v=HpovwbPGEoo

Cheers!

Have a nice Christmas and a Happy New Year!

/MarcusR

http://www.youtube.com/watch?v=cootexkM ... re=related

we should all try it.

[MarcusR]

Brilliant link daiv , I had missed that one.
Would be cool to see what it would look like for pipes

Hi Jon!
We have to see what we can do about your flute model.
It should not be that difficult to set up if one can exclude boundary layer effects and thermal conductivity.

Cheers!

/MarcusR

[Jon C.]

Ever wondered what the resonances down the flute bore looks like when you play your favorite reel or jig?

Here is a little home experiment you can do during the holidays,
all you need is a Hall crystal flute and some propane

The Rubens Tube Standing Waves:
http://www.youtube.com/watch?v=HpovwbPGEoo

Cheers!

Have a nice Christmas and a Happy New Year!

/MarcusR

Apartment dwellers probably should not experiment with this!
It really illustrates where the nodes and anti nodes form when a tone is played on a flute. This is important when designing a flute, as if there is a perturbations in the bore where the node is touching, it can dampen the tone. Notice when a complex tone was generated, how many different nod locations there would be. Luckily they already worked the flute design out in the 19th century. It would be interesting to right a program, that would show the different notes vibrating in a conical tube, to see how they are effected by the contour.

what's a node?

Nodes are where the sound wave touches the flute the anti node is the middle of the wave at th 0 point.

[withak]

The node is where the sine wave is zero, i.e. where the squiggly line on an oscilloscope crosses from positive to negative or vise versa. For wind instruments, an open hole makes a node by forcing the air pressure inside the tube at that point to be close to zero (relative to the pressure outside the tube) and creating a standing wave between the first node (the hole you are blowing into) and the second node (the hole you opened up somewhere down the length of the instrument). If you are lucky then the holes in your flute are located in such a way that the standing waves they each create correspond to a particular set of wavelengths.

There is a little more going on than that in areal life instrument though.

[withak]

edit: This is not the double-post you are looking for.

[jemtheflute]

Nodes are where the sound wave touches the flute the anti node is the middle of the wave at the 0 point.

Not quite, Jon - the "waves" in the air column in a flute are not like the oscillations of a string. Diagrams drawing them as such are just analogies for ease of visual interpretation. The air of course remains in contact with the tube wall at all times/places. The "wave" in the air-column is actually to do with varying density of the air molecules when excited and pushed around by the generation of a tone. The air is densest at nodes and least dense at antinodes. Check out these very approachable articles from Pan magazine, the Journal of the British Flute Society, contributed by physicist and flautist Robin Jakeways for a full (and properly knowledgeable!) explanation and useful diagrams. They ought to be required reading for all flute players! (We won't mention makers...... oooops, I gone an' done it!)
Hoots, Hertz and Harmonics I
Hoots, Hertz and Harmonics II
Hoots, Hertz and Harmonics III
Hoots, Hertz and Harmonics IV
Hoots, Hertz and Harmonics V
Think about it a bit - you obviously cannot make the air in a tube do what a string fixed at each end and tensioned does when plucked! Withak, I think you will find that open holes cause antinodes, not nodes - as you rightly say, the areas of least density or pressure.....

There's lots of good stuff to be gleaned about how flutes work by reading Boehm's Treatise and good old Rockstro, among others. Some of their science is outdated, but most of the fundamentals and the ways to think about how to manage the physical realities hold good.

[daiv]

this is all great! i have to go to bed now, but i'm going to look over it. i'm taking an acoustics class in the fall, and i'm trying to get a leg up on it because i think the math is going to be above me.

how's everybody's flame tubes going?

[Jon C.]

Nodes are where the sound wave touches the flute the anti node is the middle of the wave at the 0 point.

Not quite, Jon - the "waves" in the air column in a flute are not like the oscillations of a string. Diagrams drawing them as such are just analogies for ease of visual interpretation. The air of course remains in contact with the tube wall at all times/places. The "wave" in the air-column is actually to do with varying density of the air molecules when excited and pushed around by the generation of a tone. The air is densest at nodes and least dense at antinodes. Check out these very approachable articles from Pan magazine, the Journal of the British Flute Society, contributed by physicist and flautist Robin Jakeways for a full (and properly knowledgeable!) explanation and useful diagrams. They ought to be required reading for all flute players! (We won't mention makers...... oooops, I gone an' done it!)
Hoots, Hertz and Harmonics I
Hoots, Hertz and Harmonics II
Hoots, Hertz and Harmonics III
Hoots, Hertz and Harmonics IV
Hoots, Hertz and Harmonics V
Think about it a bit - you obviously cannot make the air in a tube do what a string fixed at each end and tensioned does when plucked! Withak, I think you will find that open holes cause antinodes, not nodes - as you rightly say, the areas of least density or pressure.....

There's lots of good stuff to be gleaned about how flutes work by reading Boehm's Treatise and good old Rockstro, among others. Some of their science is outdated, but most of the fundamentals and the ways to think about how to manage the physical realities hold good.

I just knew I was going to get "called on the carpet" for my comments...
I was thinking of when I designed a wind chime, but it does make more sense that it would be air waves, rather then sound waves... I guess I should have stayed in school, instead of ditching and going to the beach!

[jemtheflute]

it does make more sense that it would be air waves, rather then sound waves...

Sure thing! Of course, almost all perceived sound for us mammals is from our aural equipment picking up sound as oscillations in air pressure. With musical instruments as sound generators, some, like strings and percussion, set a solid body of some kind in frequency-specific motion and then directly or indirectly, often amplified by use of some kind of resonant body/chamber, those vibrations are transferred to the air; most wind instruments directly set the air in vibration and the attached instrument body is chiefly about defining pitch and timbre, and somewhat about amplification in some cases. This is why the material (but not the shape) of the body of a wind instrument is of comparatively small significance compared to that of, say, a violin or a drum. The actual tone generator - the reed, lip-reed, air-reed/edge tone is important, but also very susceptible of fine control compared to say, a fiddle string or a drum-skin, where their design, material properties and set-up are very influential on the tone they generate.

[rforbes]

For a visualization I always liked the bathtub model--imagine putting your hands into a full bathtub and moving them alternately together and apart so the water sloshes back and forth. If you time your movements to build up the "peak" that forms you'll be forming a resonant standing wave analogous to the one in the flute. The height of the water wave corresponds to the increase/decrease in air pressure in an acoustic wave.

I have to admit the bathtub demonstration lacks drama compared to flaming tubes, though. Perhaps a flaming bathtub...

There seems to have been a long-standing division between the proponents of the edge-tone/vortex tone mechanism and the air-reed (Helmholtz) mechanism. Benade, in section 22.6 of his Fundamentals of Musical Acoustics seems to favor the latter...

Rob

[Jon C.]

Here is a good article by A. Benade. on tuning and acoustics of wind instruments.
http://ccrma.stanford.edu/marl/Benade/d ... 3-1977.pdf

[withak]

Withak, I think you will find that open holes cause antinodes, not nodes - as you rightly say, the areas of least density or pressure.....

True, I'm used to thinking of waves in solids where you can have tension. In air you control where the minimum point on the wave is, not where the zero is.