How does a trumpet work? - Page 10

rowuk · 09-18-2009, 05:21 PM

Quote:

Originally Posted by nordlandstrompet

Ahah!
What you are saying here is about exactly the same I tried to explain in the
world famous thread "Myth about fast air", but I used the metric term "bar"
for pressure in stead of the old fashioned and out of date term "psi".

Now, to clarify once and for all: As an example:
The lips opens and close like a valve. (aka "Vibration")

#1: Still as an example:
At low frequencies, there is a "lot" (high amount) of low pressure air (1 BAR) passing through a wide aperture.

#2: Example again:
At high frequencies, there is "less" (smaller amount) of high pressure air (2 BAR) passing through a narrower aperture.

Even if the embouchure/aperture is working like a "valve", the actual speed
of the air molecules passing through the lips/aperture is different?
#1's molecules are moving slower than #2's?

I am not filling gas on the fire, just trying to clarify if we have misunderstood anything between us earlier.

Peace & Love

I can't physically measure the speed. I can measure how long I need to empty most of the 7 liters of air that I have usable. My air is gone faster on low notes. I can probably suffocate in the upper register before I run out of air. Double C requires 3 bar - at least that is what Adolf Scherbaum had written on an LP from the 50s or 60s. I practice a lot of long tones.

You can check this yourself.

nordlandstrompet · 09-18-2009, 05:33 PM

I am fully aware of that the air tank empties faster in the lower register(s).

What I'm trying to say is: (in metric terms)
A narrow aperture with a pressure of 2 bar will have a faster movement of
the air molecules than a more open aperture with a pressure of 1 bar. (mtr per second)
(I am not talking about amount of air per second. (litre per second))

rowuk · 09-18-2009, 05:53 PM

Quote:

Originally Posted by nordlandstrompet

I am fully aware of that the air tank empties faster in the lower register(s).

What I'm trying to say is: (in metric terms)
A narrow aperture with a pressure of 2 bar will have a faster movement of
the air molecules than a more open aperture with a pressure of 1 bar. (mtr per second)
(I am not talking about amount of air per second. (litre per second))

True, if we are blowing into free space. The trumpet has more "resistance" for the higher notes. That is why we do not just blow our lips into the cup of the mouthpiece when playing high notes. There is an equilibrium of pressure in front and behind the lips. We need higher pressure to overcome the resistance. I also am not talking about volume of air.

Sofus · 09-19-2009, 05:57 AM

Hey Robin!

I missed one crucial statement that you made:

Quote:

So when I talk about closed, I am not talking about the impedance/reactance at the end of the bell.

No, that´s exactly what I mean when I
say that we use different words for things!

Also, let me once again thank you for your
generousity concerning the sharing of all
your deep knowledge about trumpet physics
with us all.
As I see it, the discussions some of us physics
interrested "freaks" take part in with you actually
DO lead to more and more knowledge, and they
certainly do NOT feel like leading to NOTHING,
at least not for me!

Last but not least: thanks for sharing the formulas!
I´ll read them as soon as my family life permits me . . .

rowuk · 09-19-2009, 06:39 AM

Quote:

Originally Posted by Sofus

.........and they
certainly do NOT feel like leading to NOTHING,
at least not for me!

Then you are not at the end of the standing wave

Like with electricity, we have to be careful if we are talking about pressure nodes or amplitude.

I would like to make one correction: for all notes in the partial series, the standing wave amplitude is zero at both ends.

http://www.phy.hk/wiki/englishhtm/TwaveStatA.htm

Standing wave - Wikipedia, the free encyclopedia
Wave equation - Wikipedia, the free encyclopedia
Helmholtz equation - Wikipedia, the free encyclopedia

This link shows how the waves develop in regards to frequency and you can imagine what happens when we add/move braces only a little bit

Sofus · 09-19-2009, 11:55 AM

A link like this one you posted is always educational to see:

Standing Waves and Traveling Waves

However, it happens to be a demonstration program that is
not complete. It doesn´t say whether it is the wave Pressure
or the wave Speed that is drawn, nor does it say whether the
ends are meating a Higher or Lower impedance.

Please also try the one beneath. There you can choose

* "from a fixed end"

OR

* "from a free end"

As you will see, the standing wave is zero at the right end
(right interface where it meets a new media) just like you said,
in one of the cases but not in the other.
When you choose "from a free end" you will see that the amplitude
of the standing wave is twice the amplitude of the incident wave at
the right end, not zero. This is pretty much what I stated earlier . . .

Standing wave (explanation by superposition with the reflected wave)

Quote:

Then you are not at the end of the standing wave

Don´t expect ever to get that far, but by the help of
people like yourself, at least one step at the time IS taken!

kcmt01 · 10-22-2009, 08:37 PM

Quote:

Originally Posted by rowuk

This thread does not address the difference between pro and student horns (at least not by me - yet). It is possible to build a horn that is not efficient, has bad intonation and very unresonant - the title of this thread is "how a trumpet works" not "why some trumpets do not work". That is a topic that I would not touch on an open forum - you always step on somebodys toes and then you learn nothing!
I have measured the polar pattern of several trumpets and discovered some very interesting things............... Stay tuned!

....

I can tell you one thing for sure and for certain... a clean student horn will sound better than the best pro model that has a layer of gunk in it. I've seen dirt that would gag a maggot.

09-18-2009, 05:33 PM	#92
nordlandstrompet Forte User Join Date: Apr 2008 Location: Norway Posts: 1,156	Re: How does a trumpet work? I am fully aware of that the air tank empties faster in the lower register(s). What I'm trying to say is: (in metric terms) A narrow aperture with a pressure of 2 bar will have a faster movement of the air molecules than a more open aperture with a pressure of 1 bar. (mtr per second) (I am not talking about amount of air per second. (litre per second)) __________________ nordlands roarmp.com "When you play an Andante, people have to cry..." Maurice Andrè Olds Recording Yamaha 731S cornet Conn V1 flugel

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