Klarinet Archive - Posting 001021.txt from 2000/03

From: Tony@-----.uk (Tony Pay)
Subj: Re: [kl] Reed's mode of vibration
Date: Fri, 31 Mar 2000 04:59:59 -0500

On Thu, 30 Mar 2000 08:10:48 -0500, bhausman@-----.com said:

> At 07:26 AM 3/30/2000 -0500, Avrahm Galper wrote:
>
> > RESULTS
> >
> > 1) During a large part of its cycle, the flow of air into the
> > mouthpiece is completely cut off by the reed This is more obvious
> > visually. The only source of light used in making the photographs
> > was the mercury arc of the stroboscope, which was placed to show
> > particularly the slit between the reed and mouthpiece. This complete
> > closure of the reed apertures is in disagreement with the
> > assumptions that the chink between the mouthpiece and the reed never
> > shuts completely. It also conflicts with statements that the
> > clarinet reed never entirely shuts off the ingress of air into the
> > mouthpiece while the instrument is sounding.
>
> I remember discussions about this on the list sometime back, and some
> people disagreeing with this observation, almost violently, in spite
> of the citing of previous experimental data similar to the above. It
> is good to have further confirmation of the truth!

An alternative view is possible -- namely, that if you set the apparatus
up so that the reed shuts, then the reed shuts; and if you set the
apparatus up so that the reed doesn't shut, then the reed doesn't shut.

And in fact, Benade ('Fundamentals of Musical Acoustics', Second Revised
Edition, Dover 1990), in a discussion of reeds and mouthpieces (section
21.2, p435), says just this. The clearest statement for our purposes is
on p442, numbered statement 2:

"The simple relationship described in statement 1 between the partials
of a tone is only observed when the motion of the reed-valve parts
themselves is of small enough amplitude that the variable, pulsating
airflow through them is never entirely shut off. Once the blowing
pressure is raised to the point where the reed is blown entirely closed
for a portion of each cycle of its oscillation, the player notices a
change of feel, the listener notices a change of tone, and the higher
partials tend to grow in a way that parallels the growth of the
fundamental."

So, if that's the 'truth', are you happy with it?-)

Or do you think that the article is challenging Benade, describing an
experiment that shows that 'shutting' is required for *any* sound to be
generated? That would of course be possible.

However, I think it's unlikely. If I use a reed that is very stiff on a
mouthpiece, I can make a quiet sound by putting a lot of air through the
system, corresponding to a vibration that never has the reed shut off
the airflow. And the opposite is also true: a reed that is very
flexible shuts almost immediately.

Benade's simple mathematical argument seems to make sense too.

I've heard it said that the German technical term 'echoton' refers to
the sort of quiet, relatively harmonic-free whisper that you get by
deliberately playing so that the reed never actually closes. This is
harder to do on a German setup than on a more open setup.

Amusingly, this was the basis of someone's, I think Alan Hacker's,
calculated insult around 25 years ago to a certain brand of English
clarinet playing, which, he claimed, wasn't *really* a *tone* at all,
but merely "an 'amplified' echoton."

Tony
--
_________ Tony Pay
|ony:-) 79 Southmoor Rd Tony@-----.uk
| |ay Oxford OX2 6RE www.gmn.com/artists/welcome.asp
tel/fax 01865 553339

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