 The Clarinet BBoard
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Author: Klarnt
Date: 2024-04-07 10:38
Hi all. I have become oddly fascinated with the workings of tone holes. Could it be observed that as a tone hole becomes smaller (in comparison to the pipe diameter) the pitch flattens? In other words it will sound as though the pipe was longer than the center of the tone hole
But if that assumption is true, how does the register key work? And along the same lines how do leaks in the key pads cause the instrument to play in the upper modes? (what is a pad leak if not an oddly shaped, small hole) At what point does a theoretical shrinking tone hole cease to lower the pitch and instead raise it via the next mode?
Can anybody with knowledge in acoustics clear this up?
Let me know if I got this all wrong
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Author: Chris P
Date: 2024-04-07 21:56
A smaller diameter tonehole will yield a flatter and poorer quality (stuffy) note compared to a larger size tonehole in the same distance along the bore.
On your typical clarinet, the C#/G# tonehole is exactly this as it's a smaller than normal diameter tonehole positioned much higher along the length of the bore compared to a full size tonehole for practical and cost reasons. The ideal location of that tonehole would be just below the tenon shoulder and going through both the socket and tenon which is doable and more costly to make. Single piece body clarinets often have this and clarinets with an articulated C#/G# mechanism have this too.
Altering the length of the tonehole with a chimney or tube will also change the pitch, quality and stability of the note that issues directly from it - typically a bushed or tonehole with a chimney will be much larger than its plain equivalent even if the venting is the same. The thumb tube is considerably larger than the side F# tonehole for the simple reason the standard fingering for F# (thumb off, xoo|ooo) is effectively a forked note as LH1 is closed and the diameter of the thumb bush is not only made wider to compensate for the extra length of the thumb bush, but to also compensate for LH1 being closed so the F# that issues directly from the thumb tube is in tune, whereas the side key fingering for F# is a fully vented note with the left thumb on the thumb tube and the side key opening a smaller tonehole at the same distance without being compromised by any other toneholes being closed below it (eg. LH1). If you close just the LH1 or thumb ring without covering any toneholes, the F# will be sharper than the sandard and side key fingerings. The same is true with B/F# with both the standard (xxx|oxo) and cross key (xxx|xo/o) fingerings as the first is a forked fingering and the second is a fully vented fingering. The Acton vent compensated for this to fully vent B/F# and altissimo D#/Eb with the standard (xxx|oxo) fingering.
The fully vented notes (those without any toneholes closed immediately below the one the note issues from) on Boehm system clarinets are from highest to lowest:
Throat Bb (both standard and side key fingerings)
Throat A
Throat G#/Ab
Open G (all fingers off)
F# with the side key fingering
F/C (left thumb only)
E/B (xoo|ooo)
Eb/Bb with side or cross key fingerings
C#/G# (even though it's compromised by having a smaller diameter tonehole)
C/G (xxx|ooo)
B/F# with the cross key fingering (xxx|xo/o)
Bb/F (xxx|xoo)
Ab/Eb
F#/C#
F/C
E/B which issues directly from the bell.
All other notes not in tat list are effectively forked/undervented fingerings as they have a tonehole closed immediately below the one the note issues directly from and the toneholes are often much larger in diameter than their fully vented counterparts.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: Chris P
Date: 2024-04-07 22:05
The speaker/register key works by allowing atmospheric pressure to enter and disrupt the air column in the bore which in turn raises the pitch of the note by a 12th in the case of the clarinet, due to it having a closed/stopped cylindrical bore so it overblows just the odd numbered harmonics instead of the full harmonic series as a flute (open cylindrical bore) or oboe (closed conical bore) does.
Placing the speaker vent in a specific location on or near to a nodal point of the air column is similar in lightly touching a string at any nodal point along its length to make it sound a harmonic at a much higher pitch than the open string (an 8ve, 12th, two 8ves, etc.). As the speaker tube is in a fixed position, certain upper register notes are stronger than others and its position is a compromise to keep things simple in terms of mechanisms as ideally you'd want a speaker vent for nearly every note to make it sound in the upper register which would be a mechanical nightmare if it's fully automatic, or a physical nightmare if it's a separate speaker key for every note.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
Post Edited (2024-04-08 05:01)
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Author: Luuk ★2017
Date: 2024-04-08 12:18
From http://test.woodwind.org/clarinet/BBoard/read.html?f=1&i=508450&t=508231:
Author: Luuk ★2017
Date: 2023-11-14 13:25
The register hole acts as a small leak in the bore, forcing a pressure node to develop in the standing wave in the bore, at the register hole's location.
However, each frequency has different locations of its standing wave nodes, but the register tube is fixed. Thus, the location of the register tube matches only one 'ideal' node location. Frequencies with a pressure node at this location will be fine, but a node of a standing wave located nearby the register tube will be more or less 'pulled' in the direction of the register tube, thus influencing the frequency of the standing wave.
Try this: play B4 with traditional fingering RT 123E|123F. Now play the same note without the register key but with the trill key second from above at the upper right (the keys normally operated with your right hand first finger - open the trill key with your right thumb - you need to rest the clarinet on your knees). This trill hole is more or less located at the ideal register tube location for B4. The resulting note will feel very different from the traditional one (result depends on the clarinet). Also, try the same trick with C5 and the most upper trill key.
The mismatch of the location of the register tube for almost all frequencies except one is a problem for all instruments relying on this mechanism, oehler clarinets included, and not only clarinets.
A solution is to introduce more than one register tube, as may commonly be seen on the oboe, the saxophone and bass clarinets. This does not solve the problem completely, but makes the mechanism complex.
Please note that location of the register tube, polycylindrical designs etc. only present second or lower order deviations from the basic idea: a cylindical tube, closed at one end. For an introduction see https://newt.phys.unsw.edu.au/jw/clarinetacoustics.html
Regards,
Luuk
Philips Symphonic Band
The Netherlands
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Author: Chris P
Date: 2024-04-18 01:15
Probably somewhere around upper register D or Eb.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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