Blowing machine

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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

My next quibble is what to accept as the bottom of the xxx ooo low regime. I investigated what happens as you slowly increase flow from zero. Below you'll see the pitch of the note eg G5 minus 40 cents, and the flow needed to produce that, given as @ 2 L/Min.

Below 2, nothing. A very quiet
G5 -40 kicks in @ 2, reaching a still very wafty, quiet,
G5 @ 4.5 This all has the air of a spurious, wafty, unreal response. This then cracks back to

B4 - 27 @ 5, then, as flow is increased, it slowly winds up the pitch through
C5 @ 6
C#5 @ 6.4
D5 @ 6.7,
D#5 @ 7,
E5 @ 7.5
F5 @ 8, reaching
F#5 @ 9, finally working it's way up to
G5 @ 16, then cracks to

F#6 @ 18, fading up to
G6-20 @ 30, then cracking to the third regime

I tried this on other whistles and can produce the same sort of effect. But when I play the same whistles by mouth, I can't get below about F#5 when I can't blow any lighter unless I don't close my mouth over the beak so that some of the flow gets away.

So, ignoring the spurious ultra low response, the low regime covers a pitch range over 7 semitones and a flow rate change from 5 to 16 L/Min, whereas the 2nd regime covers less than a semitone, produced by an 18 to 30 L/Min flow.

What do we do now?
trill
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Re: Blowing machine

Post by trill »

Terry McGee wrote: Sat Jan 28, 2023 1:04 amWhat do we do now?
Terry,

A few questions:

1) how many pressure regulators are in your air-line ?

2) what are they "set" to ?

3) if they are shown, what are the make+model of the regulators ?

Thanks very much,
trill
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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

OK, here goes.

We shouldn't forget that the compressor itself is a form of pressure regulator in that it kicks out at a specific pressure and then kicks back in when that pressure has dropped a bit. Unfortunately, its pressure gauge has died long ago so I can't tell you what those pressures are! But it probably doesn't matter as the first regulator will sort that out.

Next we come to the first regulator, in the machine lathe room with the compressor. It's an AW30-02B and is currently set to 320KPa (46PSI) for general safe workshop use. (It can be set much higher!)

The second regulator is in the lab, to provide convenient local control and to safeguard following lab items from overpressure. It is an AFR-2000 and is currently set very low at about 10PSI / 70KPa. (It would benefit from having a much more sensitive pressure meter!) I tend to set it to the minimum pressure that permits the rest of the system to work.

Information, images and manuals for both of these filter regulators can be found on the Web, eg:
https://www.unitedtoolsdandenong.com.au ... 5318923451
https://cononmotor.com.au/product/aks-f ... ator-copy/

After that, the controlled pressure is fed to an Air Flow Regulator which unfortunately doesn't seem to bear any visible labelling. It's like a small tap with a very fine thread and lots of turns to give fine control. I tweak it to set the flow rate through the flow rate monitors and then on to the whistle-under-test.

Hope that makes sense and let me know if you want more info or for me to try other settings or other approaches!
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Re: Blowing machine

Post by Tunborough »

Terry McGee wrote: Sat Jan 28, 2023 12:13 am Still struggling to work out how best to tune the whistle connected to my air-blowing rig. I'm accepting Hans' suggestion to tune to the note G (It's nicely placed in the middle of the tube, and generally a fairly solid note). But at what pressure/flow to tune it to G?
For my purposes, I'd like to see the slide set so G is in tune when mouth-blown, as you would play it in a tune. That gives us our reference geometry. Then we use the blowing machine to study how the whistle behaves with that geometry. (WIDesigner has settings for air temperature and humidity, and even air pressure. The blowing machine helps us test and calibrate the model, then we change the air settings to see what the whistle might do with warm, moist air.)
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Re: Blowing machine

Post by Tunborough »

Terry McGee wrote: Sat Jan 28, 2023 1:04 am My next quibble is what to accept as the bottom of the xxx ooo low regime.
...
ignoring the spurious ultra low response, the low regime covers a pitch range over 7 semitones and a flow rate change from 5 to 16 L/Min, whereas the 2nd regime covers less than a semitone, produced by an 18 to 30 L/Min flow.

What do we do now?
Wow. Good question. The model matches your mouth-blown experience (and mine): the lowest frequency in the first register would be around 740 Hz, just above F#5. It's fascinating that the blowing machine opens up this huge range below that. (The sounds at very low air flow are called aeolian regimes; it is interesting that the blowing machine can produce them, although they aren't relevant to our musical interests.) Do you notice any changes in the quality of the sound as you go from 5 to 9 L/min? Anywhere we can draw a line in the sand?

I wonder, is there a lower limit to how low a steady air flow we can produce when blowing a whistle?
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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

Ah, yes, Aeolian regimes works. In earlier times they had an "instrument" called the "Aeolian Harp". It was a box with strings and a soundboard, and was sat in a window pinned by the window being lowered onto it. The strings were tuned to a chord, and as the breeze altered speed and direction, harmonious notes would issue from the box. I reckon it would quickly drive me nuts!

Wind on telegraph wires is another example - that's the bass instrument in the family! And of course our Banshee is the edge-blown flute. I can still remember mum hearing the wind whistling around the house as I was growing up in Australia mumbling "Jesus, Mary and Joseph, look after us". Seemed to work as we never came to any harm from Fairies.

I remember hanging around the Pizza shop down at Malua Bay one windy day and being puzzled by long notes. I tracked it down to a metal tubular pole bearing a no-parking sign at the end of the cul-de-sac. Various other signs had been attached to the pole over the years, but since taken down. That left holes where they used to be screwed, and the strong sea breeze was enjoying playing the flute they created. I joined in, covering the holes and changing the pitch. Other people waiting for pizzas were puzzled. I did wonder if I should attempt to make an aeolian flute as a piece of public art.

But on to your question. Yes, I've just been down and traversed the country between 5 and 9 L/Min. I reckon I could describe the tones below F#5 as "hollow, vague, lacking conviction". From F#5 up, they gain "a sense of purpose". Not much to pin a scientific study on, I know.

And just tried monitoring them on a Spectrum Analyser app called Advanced Spectrum Analyzer PRO. It conveniently shows the frequency of notable peaks. As I track it from the lowest pressures I can see a sudden rise in level leading up to around the 740 Hz mark where it starts to taper off, rising only slowly as I go on to the G note. So I guess we need to determine some way of defining that point.
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Re: Blowing machine

Post by Terry McGee »

Oh, and to your final question: "I wonder, is there a lower limit to how low a steady air flow we can produce when blowing a whistle?", I am getting better at blowing lightly, but I struggle to play a stable F# on the G fingering.
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Re: Blowing machine

Post by trill »

Terry McGee wrote: Sat Jan 28, 2023 5:13 pm OK, here goes. . . . Hope that makes sense . . .
Terry, my good sir,

thank you for all the detail and info ! It's exactly what I was hoping for :).

Honestly, I'm wondering if the last step-down in pressure ("10PSI / 70KPa.") will influence pitch.

The step-down will cool the flowing air. I think that might lower the pitch (compared to someone breathing). I'm hoping to estimate "how many cents" lower.

More from me when I figure it out . . . (I'm digging through notes I haven't touched in decades !)

And . . .
hans wrote: Thu Jan 19, 2023 2:50 am. . . I was always aiming to optimise my design, so that the whistle would speak easily, with little pressure . . .
Hans, I remember very well one of your Low D whistles on tour. Indeed, very easy blower, and with tremendous richness in the low notes. Felt like a purring cat. I swear, I felt the vibrations in my fingers+lungs !

trill
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Terry McGee
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Re: Blowing machine

Post by Terry McGee »

I guess we could consider running the air through a warming bath. But it would be a bit tricky. Higher airflows would require more warming than lower airflows. Woah.
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Re: Blowing machine

Post by david_h »

If you don't measure the temperature awkward people will query it's potential effect. If it isn't changing much maybe you needn't worry. Awkward people may dispute the 'much' but you will then know the range of temperatures so perhaps can test across it, establish the relationship to pitch, and make a correction.

(and then, do you have a barometer? ...)
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Re: Blowing machine

Post by Tunborough »

For comparison, here are results from a model that considers air temperature, humidity, atmospheric pressure, and even CO2 content, applied to D5 on a Feadog Mk 1. I chose D5 rather than G5 to reduce the impact of playing tendencies: I expect most of us would play that note somewhat close to the breakpoint to the second register.

If we adjust D5 to be in tune at 27 C, 100% R.H., around 300 m above sea level, 40,000 ppm CO2:
At 27 C, 100% R.H., same elevation, 400 ppm CO2, D5 will be 16 cents sharp.
At 27 C, 50% R.H., same elevation, 400 ppm CO2, D5 will be 11 cents sharp.
At 20 C, 50% R.H., same elevation, 400 ppm CO2, D5 will be 12 cents flat.
At 20 C, 100% R.H., same elevation, 40000 ppm CO2 (assuming we could obtain air like that), D5 would be 25 cents flat.

At sea level, all the results might theoretically be a fraction of a cent sharper, but any such effect would be totally buried by other slight differences in measurement.

Note that the impact of the change in CO2 content is as significant as using cooler air, and in the opposite direction. In the grand scheme of things, these are not huge differences in tuning.
trill
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Re: Blowing machine

Post by trill »

Tunborough wrote: Mon Jan 30, 2023 9:11 am. . . results from a model that considers air temperature, humidity, atmospheric pressure, and even CO2 content . . .
Wow ! Even chemistry ! All at once ! Totally impressive !

Question: what is the "model" ? Open source ? Available for sale ?

And, of course, thank you for the data putting these effects into perspective !

trill

ps: I was getting stuck with terms like "adiabatic" and "Joule-Thomson" :)
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Re: Blowing machine

Post by Tunborough »

The model is in WIDesigner: https://github.com/edwardkort/WWIDesign ... parameters.
trill wrote: Mon Jan 30, 2023 10:05 am ps: I was getting stuck with terms like "adiabatic" and "Joule-Thomson" :)
OMG, if this keeps up we'll be going through Carnot cycles. :o
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Re: Blowing machine

Post by Terry McGee »

Tunborough wrote: Mon Jan 30, 2023 9:11 am I chose D5 rather than G5 to reduce the impact of playing tendencies: I expect most of us would play that note somewhat close to the breakpoint to the second register.
That's an interesting and possibly helpful suggestion, Tunborough, and may lead us to a protocol for setting the blowing machine.

I've been making a whistle these last two days. Up to now I've only had thin whistles, Eg Killarney, Feadogs, Generations etc and a fairly fat one - my heavily tweaked Mellow D. I find the thin ones to thin sounding for me, unless perhaps for tentatively trying out tunes I don't know well enough to risk exposure. The heavily tweaked Mellow D is a bit strong for indoor use in a resonant space, but great for rooms with lots of furnishings or those pubs with acoustic tile ceilings! And for outdoors. So I've been wondering about one in the middle and decided to make one up with a 12.7mm bore. Bit of a gamble, I had nothing really to go on, but it worked out pretty well, and does lie between the others in loudness, ease of blowing top notes, etc.

And I was a bit intrigued by the question of those aeolian (low wafty low-pressure) notes. Would my new whistle which has a curved windway also exhibit them? And how close to overblowing low D do I blow as standard? And is it similar on the blower?

So I can report yes and no on the first question. I couldn't get the ultra-low-pressure totally-wafty regime that the Feadog Mk 1 could do. But maybe who cares, as it's too quiet to be noticeable, and impossible to play by mouth. With the benefit of the blower's fine flow control, I can easily convince the low regime on XXX XXX to start at F4 (350Hz), drift slowly upwards under increasing pressure through F#4, G4, G#4 , A4, Bb, B then to C#5 (556 Hz) where it started to sound real, to D5 (587.5 Hz), finally cracking to D6 at D5+10cents (591 Hz) to the second octave. So it's real, and not just a feature of that other whistle.

While all this was happening, I kept an eye on the Volume readout. At F4, it read 0%. A4, 3%. It really accelerated as we approached C# 5 to 99% and remained at that setting. Bit odd to measure sound in %, I know, and I imagine that there is an automatic gain control somewhere in the system, stopping it rising beyond 99%. But maybe we could use that or something else like it to set the threshold "what do we take as the bottom of the low regime" frequency? We do have to be aware that its distance sensitive!

In terms of where I blow D5, it's about 20 cents short of breaking to D6. If I switch Auto off on the tuner, and lighten up pressure, I'm struggling to keep playing below about D5-50. You certainly would never play down there.

Now, here's a question. Do we have to be able to set a low regime bottom for your modelling purposes? Would it be enough to know the break points to and from the upper regime?

Or can you suggest a protocol which we could use to set up the blower?
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Re: Blowing machine

Post by Tunborough »

I've got a handle on what we can say about the low, "unconvincing" part of the first register, but I regret I won't have time to assemble an explanation for a couple of days. I can say it's a feature of all whistles, not a fluke, and a very interesting feature. We don't need to look at it for all whistles, but I would like to study it carefully on a few. It could lead to refinements to the model.
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