Klarinet Archive - Posting 000730.txt from 1998/02

From: "Mr. Sheim" <fsheim@-----.com>
Subj: Re: Re[2]: Acoustics of the Primitive Early Clarinets
Date: Thu, 19 Feb 1998 18:41:28 -0500

If I remember correctly, doesnt it have something to do with an open or
closed ended pipe?

Fred (fsheim@-----.com)

At 05:03 PM 2/19/98 +0100, you wrote:
>It is a though myth that clarinet sounds do not contain even partials. A
quick
>look at some books on acoustics of musical instruments could show you this
(the
>Benade books are authoritative).
>
>Another myth is that clarinets overblow at 12th because of the cylindrical
bore.
>Flutes have cylindrical bores. The reason clarinets overblow at 12ths and
flutes
>at 8ths is the way energy is fed into the wave. In one case it is at
points of
>greatest admittance in the other at the point of greatest impedance. In other
>words the sound generating mechanism is responsable for the difference (the
>'mouthpiece').
>
>Daniel
>
>Subject: Re: Acoustics of the Primitive Early Clarinets
>Author: majordom@-----.us at #SMTP
>Date: 14/2/98 8:09
>
>
>I have been drinking a very fine Italian red wine for the past hour--a
>vintage new to me, something called "Riunite"--and under its sublime
>influence have finally worked up enough courage to answer a question,
>posted on this list, for which the truth is known but quite difficult to
>explain. "Delete" now, or bear with me, it will become clear.
>
>Earlier this week Dan Leeson posted a note about early clarinets which
>made the statement that it is harder to get a viable second register out
>of a clarinet, overblowing at the 12th, than out of a
>flute/oboe/bassoon/recorder/Saxophone/Rothophone/Sarrusophone, all of
>which overblow at the 8ve. This was challenged by another
>correspondant, but the statement is true, and has its basis in the
>behavior of air columns.
>
>Think of the vibrating air in a woodwind bore as being in an equilibrium
>state. If there is no equilibrium, there is no security to the note,
>the note respnds poorly, is stuffy, is mistuned. The desired
>equilibrium is maintained by cooperation between various
>partials--almost the same as "overtones"--which collaborate to feed
>energy into the air column in what is called a "regime of oscillation".
>In the list of instruments above **except** clarinet, these partials
>occur at frequencies of n(x), where n is an integer and x is the
>fundamental frequency. Thus for middle c (256.2 hz, which I shall
>approximate as 250 for this discussion), partials for an oboe are appx.
>250, 500, 750, 1000, 1250; which are the frequencies of the fundamental
>c and its overtones, c', g', c'', e'', etc. If you finger a low c on
>the oboe and successively overblow, you get these pitches; a register
>key has the same effect.
>
>For the clarinet, with a cylindrical rather than conical bore, n assumes
>only ODD values. Just believe this, it is true. Thus, for three finger
>c on a c clarinet, the partials are 250 (c), 750 (g'), 1250 (e''), etc.
>(note how these pitches correspond to the finger patterns on the
>clarinet!!--three fingers give c, with register gives g', with register
>and first finger raised gives e'') SInce the cut off frequency--above
>which frequency no energy is put into the system--of a clarient is about
>1500 hz, the second partial of a three finger note on a c clarinet, g'
>(750 hz) has only two vibrational frequencies feeding energy into the
>system to maintain an equilibrium, these being at 750 and 1250. A minor
>bore error or a mouthpiece problem or a shit reed which mistunes but one
>of these partials can thus make the note g' very unstable, mistuned,
>hard to attack, or all of the above.
>
>On the oboe, for the same situation, the seocnd partial (c' not g'!!)
>will have 500, 750, 1000, 1250 all feeding energy into the system,
>smoothing over discrepancies (not that oboe players ever have reed
>problems..) and STABILIZING the note.
>
>THus, the second register of a clarinet IS less secure in its behavior
>than is that of an oboe (etc). And there is a logical reason why this
>is so.
>
>I hope this rather simplified technical discussion sheds more light than
>heat; for further details, as always, look at the articles in the New
>Groves on Acoustics and at Art Benades Fundamentals of Musical
>Acoustics.
>
>And now to bed.
>
>Robert Howe
>
>