Free Reed Research

[aeolina]

I am cooperating with a bagpipe making friend who has been undertaking observational studies of double reeds behaviour using slow-motion digital video captured with a microscope camera. With his system set up we thought it would've interesting to capture footage of free reeds in action. I am obviously particularly interested in the concertina.

 

Can anyone advise us of any work of this nature done by others? 

[aeolina]

This looks promising:

 

 

[aeolina]

... and this set up:

 

 

Has anything similar been done with concertina reeds?

[Michael Eskin]

Not free reed exactly, but analysis of a Uilleann pipes chanter reed (free-vibrating double reed in a closed chamber), thought you might find the methodology possibly useful:

 

https://mma.pages.tufts.edu/musiceng/research/uilleann_pipes/uilleann_reed.pdf

 

 

 

[aeolina]

Michael, thanks for that. My colleague Philip Westwell is already aware of the work and regards it as significant. Do you know if the author/pipe maker came to apply any of these findings in his practical manufacture?

[aeolina]

Tonight we did our first quick, and satisfactory, test of viewing and activated concertina reed under oscilloscope lighting to observe it's behaviour. We will now make a proper chamber in which we can film the movement in extremely close detail. 

 

If any professional reed makers would like to have their products subjected to such scrutiny please get in touch.

[alex_holden]

6 hours ago, aeolina said:

Tonight we did our first quick, and satisfactory, test of viewing and activated concertina reed under oscilloscope lighting to observe it's behaviour. We will now make a proper chamber in which we can film the movement in extremely close detail. 

 

Do you mean strobe lighting? I do that sometimes with a handheld strobe to see how a reed is bending and how far it moves at varying pressure levels, but I haven't had great results trying to film it because the camera sensor doesn't capture the flashes the same way the human eye does. The thing it doesn't really show you is the reed startup phase, i.e. what happens in the first few milliseconds after you press a button.

[aeolina]

Alex, yes, strobe lighting. I'm confident we will get some useful film and will think on how we might address the difficulty of capturing the startup phase. 

 

Am I correct in assuming the profiling of concertina reeds is intended to influence their bending behaviour and, as a consequence, both their technical efficiency and the set of partials that determine their timbre? If so, it would be interesting to compare captures of  an unprofiled reed and an identical but profiled one. Could this help makers in making profiling decisions?

 

Have comparisons of profiled and unprofiled reeds been made through analysis of their harmonic outputs? That would be easy to do at the same time. 

 

I'm sure I did this with a reed outside and then inside the concertina when I was a student, using the equipment in the linguistics departments of two universities in Edinburgh. I can't find the printouts from that but will reproduce the test. I should really do a comparison of my lovely Aeola and my new accordion reeded Caledonian.

 

Stuart

 

 

[Clive Thorne]

With digital cameras the sensor is scanned rather than being all read simultaneously, so diffent areas of the phot are actually captured at different times,which I think is what Alex was getting at (Correct me if I'm wrong Alex). A good example of the effect can be seen if you point your camera at the propeller of an aeroplane. With a strobe light you will see the propellor blade as its proper shape. On a digital camera you will see the blade distorted into an arc, because by the time the second row of the array is scanned the propeller will have moved on very slightly, and so on. You may see the same effect if trying to photograph a reed in motion. Possibly expensive cameras do not suffer from this effect so much.

 

 

[alex_holden]

14 hours ago, Clive Thorne said:

With digital cameras the sensor is scanned rather than being all read simultaneously, so diffent areas of the phot are actually captured at different times,which I think is what Alex was getting at (Correct me if I'm wrong Alex). A good example of the effect can be seen if you point your camera at the propeller of an aeroplane. With a strobe light you will see the propellor blade as its proper shape. On a digital camera you will see the blade distorted into an arc, because by the time the second row of the array is scanned the propeller will have moved on very slightly, and so on. You may see the same effect if trying to photograph a reed in motion. Possibly expensive cameras do not suffer from this effect so much.

 

Here's an example, recorded on an iPhone:

https://www.instagram.com/p/CtQ0AFpoBSP/

 

I did wonder if a video camera with a "global shutter" sensor would work better, but I don't have one to try it.

[alex_holden]

23 hours ago, aeolina said:

Am I correct in assuming the profiling of concertina reeds is intended to influence their bending behaviour and, as a consequence, both their technical efficiency and the set of partials that determine their timbre? If so, it would be interesting to compare captures of  an unprofiled reed and an identical but profiled one. Could this help makers in making profiling decisions?

 

Profiling is necessary because otherwise bass reeds would need to be extremely long, and I suspect very high reeds wouldn't work at all because they would need to be too short and stiff to start at normal air pressure. The scale defines (among other things) the length for each pitch. Bass reeds have a thick tip and a thin root and high reeds have a thin tip and a relatively thick root (that's a bit of an oversimplification). Somewhere in the middle of the range you end up with a profile that is roughly parallel. Once you get a profile that produces the correct pitch there is some leeway to adjust the profile to alter the stiffness of the reed. For me that process is more about enhancing the responsiveness, dynamic range, and balance across the instrument rather than deliberately affecting the timbre.

[Richard Mellish]

14 hours ago, Clive Thorne said:

With digital cameras the sensor is scanned rather than being all read simultaneously, so diffent areas of the phot are actually captured at different times,which I think is what Alex was getting at (Correct me if I'm wrong Alex). A good example of the effect can be seen if you point your camera at the propeller of an aeroplane. With a strobe light you will see the propellor blade as its proper shape. On a digital camera you will see the blade distorted into an arc, because by the time the second row of the array is scanned the propeller will have moved on very slightly, and so on. You may see the same effect if trying to photograph a reed in motion. Possibly expensive cameras do not suffer from this effect so much.

 

 

That problem may not exist when the only illumination is a strobe lamp, because then all parts of the sensor see the object illuminated at the same brief instant, even though the information is then read out from the sensor row by row. Alex's video seems to show what the reed actually does.

[alex_holden]

11 minutes ago, Richard Mellish said:

That problem may not exist when the only illumination is a strobe lamp, because then all parts of the sensor see the object illuminated at the same brief instant, even though the information is then read out from the sensor row by row. Alex's video seems to show what the reed actually does.

 

Interesting point. I suspect the brighter stripes might have something to do with the progressive readout: perhaps that area is capturing two strobe flashes instead of one?

[aeolina]

3 hours ago, alex_holden said:

 

Here's an example, recorded on an iPhone:

https://www.instagram.com/p/CtQ0AFpoBSP/

 

I did wonder if a video camera with a "global shutter" sensor would work better, but I don't have one to try it.

Nice video. I hope to have some results soon.

[Clive Thorne]

I guess that if there is a problem with the scanning time of the sensor then, in terms of reeds, it would be more apparent at higher frequencies. I should point out that my propeller blade example is based on the camera in an 8 year old Samsung phone. I'm sure that things have moved on somewhat in the meantime!

 

I've just had a look on the web for information about digital camera scan times, different sensor types etc and, to be honest, it seems more complicated than I can be bothered to take in for the sake of this thread (concertina to play etc).

 

Best wishes for your project!

 

[aeolina]

Here are our first results. Hopefully I have given the correct technical information.

 

http://raretunes.org/free-reed-research/

[alex_holden]

1 hour ago, aeolina said:

Here are our first results. Hopefully I have given the correct technical information.

 

http://raretunes.org/free-reed-research/

 

I think strobing at twice the reed frequency is giving you a double image, i.e. the camera is simultaneously capturing both the upper and lower half of the cycle.