Klarinet Archive - Posting 000727.txt from 1998/02

From: Daniel.Meirsman@-----.com
Subj: Re[2]: Acoustics of the Primitive Early Clarinets
Date: Thu, 19 Feb 1998 11:03:40 -0500

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 t=
his (the
Benade books are authoritative).

Another myth is that clarinets overblow at 12th because of the cylindri=
cal bore.
Flutes have cylindrical bores. The reason clarinets overblow at 12ths a=
nd flutes
at 8ths is the way energy is fed into the wave. In one case it is at po=
ints 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 t=
o
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 ou=
t
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 equilibriu=
m
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 assume=
s
only ODD values. Just believe this, it is true. Thus, for three finge=
r
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 abou=
t
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 mino=
r
bore error or a mouthpiece problem or a shit reed which mistunes but on=
e
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 tha=
n
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
=