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#1 2010-08-20 18:23:34

PSmith
Member
From: Vancouver, BC
Registered: 2008-09-08
Posts: 29

Rounded edge at Ro

There has been a lot discussed about rounded finger holes. For instance http://www.shakuhachiforum.com/viewtopic.php?pid=28957

I am interesting on people's experiences and comments about rounding the edge at the bottom of the shakuhachi. I am not talking about flaring out the bottom, but just rounding off the edge.

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#2 2010-08-20 19:04:37

edosan
Edomologist
From: Salt Lake City
Registered: 2005-10-09
Posts: 2185

Re: Rounded edge at Ro

PSmith wrote:

There has been a lot discussed about rounded finger holes. For instance http://www.shakuhachiforum.com/viewtopic.php?pid=28957

I am interesting on people's experiences and comments about rounding the edge at the bottom of the shakuhachi. I am not talking about flaring out the bottom, but just rounding off the edge.

WHICH edge? Do you mean the edge at the bore opening on the root end?


Zen is not easy.
It takes effort to attain nothingness.
And then what do you have?
Bupkes.

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#3 2010-08-20 19:19:37

PSmith
Member
From: Vancouver, BC
Registered: 2008-09-08
Posts: 29

Re: Rounded edge at Ro

edosan wrote:

Do you mean the edge at the bore opening on the root end?

Yes, that one.

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#4 2010-08-20 21:16:39

Toby
Shakuhachi Scientist
From: out somewhere circling the sun
Registered: 2008-03-15
Posts: 405

Re: Rounded edge at Ro

The acoustic scientists will tell you that the only edge you should have anywhere in the bore is the blowing edge. For the rest, the rounder the better, in terms of limiting destructive turbulence and increasing acoustic efficiency.

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#5 2010-08-22 19:29:37

Derek Van Choice
Member
From: Lake San Marcos, CA
Registered: 2005-10-21
Posts: 99
Website

Re: Rounded edge at Ro

The rounded finger hole thread was/is very interesting.  PSmith's question about the edge of the root hole is a good one.  Most are visually crisp.  I wonder what the radius dimension needs to be, say, on a standard 18mm +/- opening, to get enough out of turbular flow to affect the tone?  I wish I had a "disposable" on hand at the moment to test it.

I also wonder what elements could be adversely affected by reducing that turbulence, which must create a small amount of back pressure at the kanjiri?  Would the tone better at the expense of response, just as an example?

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#6 2010-08-25 04:22:58

Toby
Shakuhachi Scientist
From: out somewhere circling the sun
Registered: 2008-03-15
Posts: 405

Re: Rounded edge at Ro

Benade says that the radius of curvature of the rounding should be more than 0.1*sqrt(250/f) mm when f = lowest frequency of the flute. For a 1.8 that works out to about 0.09mm. So a radius of curvature if less than 1/10 of a millimeter would be enough to avoid the "worst effects" of turbulence.

NO elements are adversely affected by reducing turbulence, unless you like windy sounds and lack of dynamic range. Turbulence effects kick in at a certain dynamic, and limit the possibility of going any louder. They also make the instrument seem "deader" and less responsive. Benade states that microscopic differences in edge sharpness between instruments is the single largest factor differentiating one "identical" instrument from another. He further states that several minutes of playing a new clarinet makes a noticeable difference in response due to microscopic wear at the outside of the thumb hole. I would tend to all doubt this, except for the fact that Benade is the greatest woodwind acoustician of all time, and not only redesigned the clarinet, but was famous for repair and design of woodwinds, and was an adviser to a number of major musical instrument companies, as well as winning numerous awards in musical acoustics.

Turbulence creates no "back pressure".  It simply cripples the standing wave that creates the note. It is only useful for creating weak and windy tone.

Toby

Last edited by Toby (2010-08-25 04:39:18)

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