Klarinet Archive - Posting 000580.txt from 1997/09

From: Jonathan Cohler <cohler@-----.net>
Subj: Re: Clarinet material
Date: Thu, 11 Sep 1997 02:19:36 -0400

Steve Prescott wrote:

>Jonathan,
>
> If the material of which the instrument is constructed is thin
>enough to vibrate sympathetically with the sound waves passing through it,
>will this affect the resultant pitch? I think this has more bearing on
>brass instruments (and flute and saxophone) as I don't think you can
>construct a clarinet thin enough yet strong enough to allow the material to
>vibrate.

Yes. While it is true that vibration of the walls does not alter the sound
by radiation from the walls, it is also true that wall vibrations will
alter the frequencies of the air column. To quote Benade on this:

The air column "looks" oversize at points of large wall vibration
if the natural frequency of the wall lies above that of the air
mode which drives it, and undersize when this frequency relationship
is reversed. I have seen instruments (thin-walled metal flutes in
particular) whose behavior semms perfectly insane unless the
complex influence of wall vibrations on regimes of oscillation
throughout the scale is suitably damped out.

As you point out, clarinets are normally made of material so thick that
there are no significant wall vibrations. I also believe that brass
instruments are normally made of sufficient thickness such that the wall
vibrations are insignificant. But as Benade notes above, wall vibrations,
where they exist, will have a different effect on different frequencies
(which is why it is desirable to not to have any).

>
> If the bell of a trumpet "rings" a Bb then will the instrument
>favor the associated harmonics? Will certain notes "center" more than
>others?

The centering of notes on brass instruments is controlled by the precise
bore shape and the shape of the back-bore/mouthpiece combination. This is
discussed in great detail in Fundamentals of Musical Acoustics chapter 20
pp. 391-429.

>
> If the instrument doesn't vibrate - which I don't believe clarinets
>do - the above questions would be irrelevant, I know, but I'd still like to
>know what you think about materials other than wood.
>

The materials don't make a significant difference in the sound. As I've
said before, I would love to have a nice looking plastic Rossi clarinet. I
used to play Buffet R13s, and if I had not found the Rossi a few years ago,
I would probably be an avid Greenliner at this point!

-----------------------
Jonathan Cohler
cohler@-----.net