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 Post subject: Hot Delrin!
PostPosted: Fri May 19, 2017 11:45 am 
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I have floated here in the past the theory that one of the ways material can
make a difference to a flute's sound/timbre is this: the molecular structure of the
stuff vibrates, maybe not lots, but enough to condition the vibrations of the column
of air inside the flute that makes the tone. This is rightly controversial, I appreciate,
and the theory is that molecular structure thereby contributes enough to tone
to sometimes make a discernible and particular difference (which allegedly explains why blackwood
and boxwood are widely thought to affect the sound in different ways).

I'm playing a Copley delrin flute on the street a lot. We start early in the morning, it's cold. As the day goes on the sun reaches us, the delrin flute warms up considerably. The sound of the flute changes markedly when it's warm. It's louder and (here words will fail me) a good deal more expressive. It's like playing another flute. Something is changing in the flute that accounts for this, and let me suggest the 'molecular structure' hypothesis is pretty plausible, as heat would make a difference to the strength of the bonds
tween molecules. Of course there are other alternatives--maybe heat changes the bore surface in ways that affect tone without the flute conditioning the sound by vibrating somewhat--but it seems to me, anyhow, that this is less plausible. FWIW. I don't claim that this is a slam dunk argument for my theory, but I do think it may add to its plausiblity


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 Post subject: Re: Hot Delrin!
PostPosted: Fri May 19, 2017 12:08 pm 
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A counter theory is that the heat of the day makes your tympanic membrane more vibratory, thereby increasing both the volume and sensitivity observed by the auditory nerve....

A testable hypothesis?

Best wishes.

Steve

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 Post subject: Re: Hot Delrin!
PostPosted: Fri May 19, 2017 12:20 pm 
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Another theory is that Delrin has a significant coefficient of thermal expansion in all directions (0.000068). This is forty times that of wood in a direction parallel to the grain and 4 times that of wood in the direction perpendicular to the grain (yes wood is weird). Therefore as it warms up there are changes in sounding length that affect pitch, even more so than a wooden flute. My theory is that you are changing your embouchure to compensate and at this revised embouchure you have a better tone.

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 Post subject: Re: Hot Delrin!
PostPosted: Fri May 19, 2017 1:15 pm 
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I can make no pretense that the acoustic phenomenon I mentioned (warm delrin sounds markedly different than not-warm delrin) absolutely rules out counter-hypotheses. I do think my explanation of the phenomenon is more plausible and complete than the idea that my body has changed (due to heat) so that I experience sound differently or that the sounding length of the flute has changed. Of course a lot of arguments in science etc are not coercive, but merely support their conclusion more or less. I offer this as one of those. The underlying idea is that the vibrating column of air inside the flute moves the 'walls' of the flute enough that these in turn affect (colors) the sound of that column. There is a kind of reciprocal relation tween the vibrating column of air and the (allegedly) vibrating flute. This is in turn conditioned partly by the molecular structure of the flute's material, which explains the distinctive sound of some different materials. It predicts, I think, that hot delrin will have a discernibly different sound than delrin played steadily under less hot conditions, since (I think) the molecular bonds in the delrin are somewhat affected and become more 'plastic' due to heat. I agree this is not decisive, but it counts in its favor that this simple hypothesis explains a lot. It would be nice to know more about how heat affects the molecular structure of delrin.


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 Post subject: Re: Hot Delrin!
PostPosted: Sat May 20, 2017 8:11 pm 
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These are interesting and useful observations. Is not so much the Delrin that is changing as the column of air that it holds and shapes that is changing. The long debate about the difference in one material to the other is over if the flute is considered as a container for a specific shape of the air column. This has to be defined down to the microscopic level and this is where the actual physical dimensions begin to differ and have some significance. Boxwood vs Blackwood machined and finished the same way will look dramatically different when viewed at 200X magnification. One will be more pitted than the other. These pits and the degree are what is important. Most of the acoustical effect take place in the boundary between wood and air in that the air molecules are moving against these rough or not so rough surfaces with varying degrees of friction. One would think that a smoother surface would be better but that is not necessarily so - and contraindicated by my observations on some instruments (especially Baroque flutes. The originals never had polished bores!). Thus you will get a difference in sound between two identical flutes made out of different materials and cut exactly in every aspect. It is the microscopic frictional surfaces that makes the difference in sound.

Add heat to this and that throws a curve ball into one's observations. It may be that the bore shape changes more in Delrin from the heat compared with wood. This is something that sensitive measuring tools could measure. Wood has the added complication of changing shape and to a lesser degree the microscopic shape from the breath's moisture. It may be that warming up is partly the humidity causing a closing or opening up of the wood cells surface porosity. On Delrin, the moisture simply condenses inside the bore and this has an impact on its acoustical characteristics. Take the delrin with you to a swimming pool and dip in the water with it and blow it. There is a video on YouTube of some flute player doing this with a modern flute. I might try this with one made from blackwood but Puget Sound is too cold most of the time! 4 minutes and one succumbs to hypothermia on a day in the 90s.

Casey

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 Post subject: Re: Hot Delrin!
PostPosted: Sun May 21, 2017 8:06 am 
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Of course, it could just be the changes in air temperature and humidity regardless of the instrument. Easy enough to check on a one person self observation level - take a couple of wooden flutes and a metal one along and see if you observe the same or different phenomena on them under the same variabilities of the ambient conditions.

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 Post subject: Re: Hot Delrin!
PostPosted: Mon May 22, 2017 2:29 am 
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Does air temperature and humidity influence the nature of the jet or the way a player breathes? Does flute temperature influence any condensation-related effects? Something environmental does have an effect on the presence and extent of any condensation patch beyond the aperture.


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 Post subject: Re: Hot Delrin!
PostPosted: Mon May 22, 2017 5:59 am 
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david_h wrote:
Does flute temperature influence any condensation-related effects?


Flute surface temperature very definitely has an effect on condensation within the body of the flute. If the flute surface is above the wet bulb temperature of the air and you are blowing into it, moisture will not condense on the surface; if below, moisture will. The lower the surface temperature the more moisture will condense. As Casey has noted woods will absorb a portion of this moisture to distort in different ways than Delrin, and Delrin will expand due to thermal effects differently than wood. More condensation will build up inside a Delrin flute, also changing the tone, due to its relative impermeability to moisture.

Then there is the effect on the pads (if you have them) and socket/tennon joints. I know with my antique flute with vintage leather pads (I've been afraid to change them as they do work well) I get a distinct improvement in tone after about 1/2 hr of playing. Not sure if it is just my embouchure getting tuned in better or the pads getting moist and sealing better. Someday I'll have to experiment.

It's a complicated process. I'm amazed any woodwind maker can get it right.

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 Post subject: Re: Hot Delrin!
PostPosted: Mon May 22, 2017 1:22 pm 
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Who says we can get it right? Or even care to try?

Casey

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 Post subject: Re: Hot Delrin!
PostPosted: Mon May 22, 2017 11:31 pm 
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Every time I see this thread title, my brain reads it as "Hot Delrin, Batman!"

:)

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 Post subject: Re: Hot Delrin!
PostPosted: Tue May 23, 2017 8:43 am 
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Casey Burns wrote:
Who says we can get it right? Or even care to try?

Casey


I was about to say something very similar :-) I know what Latticino means, but I don't feel like I ever get it right, which is what keeps me striving! It's like a quest....

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 Post subject: Re: Hot Delrin!
PostPosted: Thu Jun 08, 2017 6:39 am 
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When I played in a marching band as a boy the horn was completely unplayable when we went outside to practice during winter (freezingly cold). Had to blow warm air through the instrument for a few minutes to warm it up, and after that it played normally.
The only explanation I can think of (and that was anyhow what it felt like at the time) is that it's about the temperature of the air column. The ice cold metal would cool the air, and the resonance points moved away from what the instrument was designed for. Pre-blowing the instrument heated the metal enough so that it didn't suck the heat from the air I blew through it, and if I continued playing it was self-sustained. I imagine a flute would have the same issues, except that there's no (or not much) airstream, so you're more dependent on the ambient air temperature. Well, according to my humble speculations of course.


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 Post subject: Re: Hot Delrin!
PostPosted: Thu Jun 08, 2017 9:37 am 
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just a quick note that I play flutes made of wood on the street, along with the delrin Copley.
It's cool when we get there, it gets quite a bit warmer later in the day, about 11 when the sun strikes the instruments. The delrin flute is the only one which sounds markedly different when it gets hot.


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 Post subject: Re: Hot Delrin!
PostPosted: Thu Jun 15, 2017 3:54 pm 
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It seems easy enough to try warming the flute by some other method than being out in the sun and see how it plays. Have you ever tried to measure the temperature difference? A flute warmed before it was played would start off warm but without condensation.

I still have a problem with considering it proven that the material makes no difference based on studies using recordings. Recordings of the flute are not perfect replications of the sound and the quality can depend a lot on the whole recording system etc. Of course I can't see a good way to replicate the study without using recordings.


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