Finger Hole Size

This page discusses issues related to the sizes of finger holes. It also describes the parameters of the NAFlutomat tool related to setting the “Highest Intended Note” field, the effect of nodal interference, and the suggested minimum hole size.

The basic issues surrounding minimum finger hole size are described by Edward Kort (Yahoo/NFW, #17,589, December 11, 2004):

The choice of playing hole size, beyond getting the intended note to play in tune, is based on the following considerations:

1. Esthetics.
   1. Do you like the look of big holes or small holes?
   2. Do you like evenly spaced holes (of different sizes) or equal sized holes (with different spacings)?
2. Playability:
   1. Does the flute player have small fingers (and needs small holes)?
   2. Does the flute player have short or long fingers (or play with the pinkie, like me), requiring holes sizes to accommodate the needed spacing?
3. Crossfingering. If you want to get notes other than the pentatonic scale to be in tune, hole sizes will have an effect.
4. Uniform tone quality across the flute's range If the lower holes are too small, those notes will have a rough, muffled sound; for large flutes, those notes may not play at all.
5. Ability to play notes in the second octave.

The “Minimum playing hole diameter” on the NAFlutomat interface only applies to the last consideration above. If you can satisfy all your other concerns, then minimum diameter should be considered. For me, being able to play at least a minor third above the octave third is very important, so I will even sacrifice some portion of the other considerations to make it happen.

That said, the minimum hole size calculation in NAFlutomat should only be considered an approximation. The calculation is based on the assumption that all the playing holes are the same size, which is almost never the case. Nonetheless, my experience is that if the holes are made much smaller than indicated, the second octave notes will be weaker than desired. If the lowest hole is smaller than the second hole (which is quite common), you will have to half-hole the second hole when playing the octave third. Too small a hole won't allow you to play the note at all.

Again, if second octave notes are not your immediate concern, don't worry much about the minimum hole size.

Mike Prairie (personal communication, August 29, 2014) indicated that the calculation of the minimum hole size in NAFlutomat originated in [Price 1997]. Mike also noted that there are “are other nuances, like the top two open holes are really what determines the highest playable note. This is based on some transmission line theory that is explained by Benade ([Benade 1990]), and the experimental numbers that Lew [Paxton Price] came up with seem to be somewhat consistent with that theory.”

Color Coding of Hole Diameter Fields

The bottom-most “Hole diameter” fields on the NAFlutomat tool are color-coded after a calculation is performed.

The background color of the finger hole diameter fields is set for those finger holes that are within the range implied by the “Highest intended note” and the “Key of Flute selections”. The background colors of the corresponding hole diameter fields are set based on how they compare with the “Minimum Playing Hole Diameter” calculation: pink for less than the calculated Minimum playing hole diameter size, and a deeper red for less than 90% of the calculated Minimum playing hole diameter size.