Trumpet harmonics?

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Salmon Egg - 27 Sep 2006 23:07 GMT

A clarinet plays a fundamental with a wavelength close to four times the
effective length of the constant diameter tube. The tone produced that way
will have a substantial content of odd harmonics with very little even
harmonic content. By over blowing, odd harmonics can be played as well. The
physics behind this is that the tube is resonating in odd quarter-wave modes
because one end is closed while the other end is open. I understand this
well.

A trumpet or a trombone also has a uniform diameter tube except for a short
bell. I read that a trumpet is able to produce both even and odd harmonics
because it works as if it is open at both ends. Why does the mouthpiece and
the lips together not act as a closed end the way it would for a clarinet?
The only thing I can think of is that the lips do not make a good seal with
the mouthpiece so that there is plenty of room for the resonator to couple
to the outside air bypassing the lips.

If someone truly knows the answer to my question, please let me know what it
is.

Bill
-- Fermez le Bush

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Chris Whealy - 27 Sep 2006 23:36 GMT

> A trumpet or a trombone also has a uniform diameter tube except for a short
> bell. I read that a trumpet is able to produce both even and odd harmonics
[quoted text clipped - 6 lines]
> If someone truly knows the answer to my question, please let me know what it
> is.

I guess that with the clarinet, the vibrating reed creates a
sufficiently high impedance that the clarinet can be considered closed
at the mouth piece end.

I can't give you the exact physics, but having recently started playing
the trombone, I can relate my experience.

With the trombone slide fully closed (position 1) the fundamental note
from a B flat trombone is (no surprise) a B flat. However, I must
maintain the correct lip tension and mouth position in order for the
trombone to sound a true B flat.

If I relax my mouth position and open my throat, I can sound a G natural
- which is a full minor third lower than the expected note. I noticed
this a few weeks ago and concluded that the vibration of my lips does
not create a high enough impedance to close off the end of the trombone
at the mouth piece.

By altering my mouth position, I can get a range of pitches varying from
the expected note down to a minor third below the expected note (which
is probably considered very bad technique!) Maybe a more skilful player
than myself can demonstrate a wider range of notes than this.

So I conclude that the volume of air in the player's mouth/throat
contributes in addition to the slide position, to the length of the
instrument, and therefore the pitch that is produced.

I know this does not fully answer your question, but at least my
experience confirms the validity of your question.

Chris W

Signature

The voice of ignorance speaks loud and long,
But the words of the wise are quiet and few.
---

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Salmon Egg - 28 Sep 2006 05:59 GMT

On 9/27/06 3:36 PM, in article efeud9$rat$2@news.sap-ag.de, "Chris Whealy"
<moc.pas@ylaehw.sirhc> wrote:

> I guess that with the clarinet, the vibrating reed creates a
> sufficiently high impedance that the clarinet can be considered closed
[quoted text clipped - 25 lines]
> I know this does not fully answer your question, but at least my
> experience confirms the validity of your question.

Normally, a horn will not be played at its fundamental or pedal note. Do do
you know the unfolded length of your trombone in the first position? From
that it is not difficult to calculate what the fundamental frequency should
be. Starting with the lowest not you can get, what notes to you get as you
go up in frequency just by means of lip and breath control?

Bill
-- Fermez le Bush

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Natural Science Forum / Physics / Acoustics / September 2006

Trumpet harmonics?