Klarinet Archive - Posting 000178.txt from 2010/08

From: "Keith Bowen" <keith.bowen@-----.com>
Subj: Re: [kl] About clarinet acoustics
Date: Mon, 16 Aug 2010 19:18:44 -0400

The sound velocity is numerically the same as the speed of sound. I slipped
into the accurate though pedantic habit of calling it a velocity, since it
is a vector and has a direction associated with it. Oh and it's a complex
quantity too, the imaginary part representing absorption.

So yes, I stated that the speed increases in the flared portion.

You (and others in this discussion who have not done so) really need to read
Arthur Benade's classic books: 'Horns Strings and Harmony' for and
introduction, and 'Fundamentals of Musical Acoustics'. Benade states on page
406 of 'Fundamentals...' that "it should be easy to understand that sounds
propagate with different speeds as they travel through different parts of a
horn: wherever the duct walls curve outward ... the speed is greater than
the 345 m/s expected in the open air ..."

Benade does not explain this further, but I think that what is happening is
that

Speed = wavelength x frequency for any wave

Frequency is constant along the tube for any propagating wave (travelling
and self-sustaining)

Wavelength is lengthening in flared sections (see diagrams in Benade)

Hence speed is increasing to satisfy the equation.

There is tube below the tone hole but very little propagation of waves. They
are strongly damped after the tone hole, and while they can make minor
(though possibly artistically important) changes, they don't affect the
basic frequencies, EXCEPT for forked fingerings, when the end effects of a
tone hole extend beyond the position of the next closed hole.

Please see my next post also, for a further reference.

Keith

-----Original Message-----
From: Jennifer Jones [mailto:helen.jennifer@-----.com]
Sent: 16 August 2010 22:12
To: The Klarinet Mailing List
Subject: Re: [kl] About clarinet acoustics

On Mon, Aug 16, 2010 at 2:06 PM, Keith Bowen <keith.bowen@-----.com> wrote:
> Yes. The sound velocity will increase in the flared portion

How does the sound velocity increase? What is "sound velocity"? Is
this the speed of sound?

- though I'm not
> sure by how much. Another reason for making the measurement to a tone hole
> in the parallel part (and applying the end correction, which is quite
> large).

The problem with this is that there is still tube below the tone hole
in the fully assembled clarinet, isn't it?
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