Klarinet Archive - Posting 000436.txt from 2002/05

From: Roger Shilcock <roger.shilcock@-----.uk>
Subj: Re: [kl] Turbulence (was, "grunt")
Date: Fri, 17 May 2002 06:10:51 -0400

Isn't it the case that many saxophone mouthpieces are designed so as to
*increase* this sort of turbulence deliberately?
Roger S.

In message <20020517.085031.92@-----.org writes:
> Audrey wrote, about her 'grunt':
>
> > Being an amateur, I probably can't help much with how it works, though
> > Morrie can.....HEEEEEELLLLP, MORRIE! I can describe what it looks
> > like, though: it looks like a long, sharpened pencil lead with the
> > thicker end attached to the middle of the register key pad. It goes
> > in and out as the register key is opened and closed. Why it works I
> > don't know, but it does, and I'm delighted with it.
>
> One of the things that gets in the way of efficient operation of a wind
> instrument is turbulence. Turbulence is very often characterised by the
> simultaneous presence in the system of many frequencies of vibration;
> energy that would otherwise emerge as musical sound emerges instead as
> 'noise'.
>
> Aircraft, too, have to minimise turbulence in order not to waste energy;
> that can sometimes be achieved by making slight changes to the geometry
> of the wing. These changes help the airflow to be smooth, instead of
> broken up.
>
> A good, everyday example of turbulence is the flow of water from a
> simple tap (faucet). If you turn on a tap to medium flow, then the
> water exits in a smooth cylinder. Increasing the flow rate, you can
> observe that at a certain critical point the smooth surface of the water
> breaks up, and the flow becomes turbulent.
>
> You can delay the onset of this turbulence by rounding the edge of the
> inside of the tap, where the water exits. Sharp 'corners' tend to
> encourage turbulence.
>
> Analogously, you can improve the 'ring' of a clarinet at louder dynamics
> by rounding the sharp edges that the airflow encounters, both inside and
> outside the instrument. (We're talking about a very tiny amount of
> rounding here, almost invisible to the naked eye. It's nothing that
> could possibly affect intonation.) The effect is that you can get to a
> higher dynamic before the sound starts to break up -- just as you can
> get to a higher flow rate in the tap before the smooth stream of water
> starts to break up.
>
> Remember, in the case of the clarinet, we're not just talking about
> turbulence in the passage of air down the instrument. It's turbulence
> in the forwards and backwards flow of air implicit in the *vibration* of
> the whole aircolumn that has the sound 'break up' at higher dynamics.
> So, actually, the quality of the instrument at lower dynamics can be
> affected too.
>
> It's been suggested that one of the differences between the response of
> wood clarinets in general and the response of metal clarinets in general
> can be traced to the different degree of 'rounding' that different
> manufacturing techniques tend to produce.
>
> It's also why instruments 'go' better when they're warm than when
> they're cold. The onset of turbulence is temperature-dependent (it
> occurs earlier at lower temperatures), so the 'dull' response of your
> instrument on a cold day has a physical basis.
>
> Much of this is covered in Benade, pp 500/501.
>
> So finally, I imagine that the 'grunt' is one of those small alterations
> of geometry that help the airflow round the pad not to be turbulent. In
> this case it isn't a question of the turbulence interfering with the
> vibration of the instrument; it's just that it makes a noise that you
> don't want.
>
> Tony
> --
> _________ Tony Pay
> |ony:-) 79 Southmoor Rd Tony@-----.uk
> | |ay Oxford OX2 6RE http://classicalplus.gmn.com/artists
> tel/fax 01865 553339
>
> ... urble wurble.. very small chaps, but immensely powerful... urble... etc.
>
> ---------------------------------------------------------------------
>
>

--
You must not whinge about getting old. But you can swear.
------------ Barbara Castle

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