Klarinet Archive - Posting 000672.txt from 1998/09

From: "Dee Hays" <deerich@-----.net>
Subj: Re: [kl] Pitch standard confusion
Date: Sat, 19 Sep 1998 10:48:43 -0400

-----Original Message-----
From: Matt Palasik <mattp169@-----.com>
Date: Friday, September 18, 1998 10:10 PM
Subject: Re: [kl] Pitch standard confusion

>i think my point is being misinterpreted. Instruments are disigned to
>play at the standard a@-----. but often
>enough the temp is not 72 degrees where you perform. and the difference
>in temps is great from freezing cold to extremly hot. and i believe Ed
>lacypointed out that many orchestras etc will tak ethe temp in to
>consideration hen tuning. Which makes sense. But my point is is there
>a way to manufature instruments so they may be better in tune at the
>varying temps. Maybe using a different sythetic material or something or
>some way of changing the instrument design to accomadate varying
>temps.
>

No there is not a way to design instruments to accomodate the varying
temperatures other than things like pulling the barrel or adjustable barrels
or tuning slides (like the brass) as is currently done. The change in pitch
is NOT due to the expansion or contraction of the material. The coefficient
of thermal expansion is so small that over the range of temperatures that
the instrument sees, the change in length is insignificant. For example,
the coefficient for aluminum is approximately 0.00001 inches per inch per
degree Fahrenheit. Now if you had an aluminum clarinet that was 24 inches
in length and the temperature went from 32F to 102F the change in length is:

26 x 70 x 0.00001 @-----.0182 inches of growth going from cold to hot

This is 0.07% change in the total length. Thus it might affect the pitch by
0.07 cents. And it since the length grows going from cold to hot, the pitch
would be going down not up if it were due to changes in the length of the
instrument.

The reason that I use aluminum in the example is that I happen to know its
coefficient and it expands more than most metals due to temperature.

The coefficient of thermal expansion for wood is substantially below that of
any metal. So temperature induced changes in the instrument length are not
the cause of tuning problems in hot or cold rooms.

It is however due to the properties of air. The speed of sound in air
changes dramatically with temperature. The frequency (or pitch) is the
result of the speed of sound divided by the wave length. We pick our notes
on the clarinet and other musical instruments by picking a length (i.e.
covering the holes). The length has not changed significantly (as shown
above) but the speed of sound does. And thus so does the frequency. It is
true, that your breath will have a constant temperature (relatively) but
when the sound wave exits the horn, it will hit the hotter/colder air and
respond to the different density that it encounters. The wavelength as
generated by the instrument will stay the same but the frequency must then
shift to due to the speed of sound in the air.

If the change were due to changes in the instrument length, they would get
longer in the heat (i.e. flatter) rather than sharper as is the case in the
real world. Notice how much players have to pull their barrel or tuning
slide on a hot day to match an electronic tuner. They don't push them in
unless they have pulled them too far in the first place.

Dee Hays
Canton, SD

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