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No air thru the horn


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kalijah
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PostPosted: Wed Aug 03, 2022 2:36 pm    Post subject: Reply with quote

Quote:
The demo in the video here shows sound can be made with a membrane without pushing air through but at no point does it match the tone of a normally played horn.


Obviously this set-up is acoustically inferior to a normal and complete instrument as some of the acoustic energy of is lost through the vent. The membrane also likely limits how much can be transmitted.

Notice the "vent" that allows air to flow out of the side of the mouthpiece cup must have some flow resistance. This allows the air pressure to rise on the air pulsation sufficient to play a tone. The pressure in the cup rises and deflects the membrane at a high enough velocity to create a pressure wave on the downstream side, which then transmits through the instrument.
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tptptp
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PostPosted: Wed Aug 03, 2022 2:59 pm    Post subject: Reply with quote

Tom LeCompte wrote:
Physicist. 1628 papers, 211,760 citations.


Impressive! In my field, I did my main thing about 12,000 times over 40 years, but only wrote one paper.
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huntman10
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PostPosted: Wed Aug 03, 2022 4:39 pm    Post subject: Reply with quote

C'mon man! 1,628 papers. One a week for 30 years? Seriously?

Maybe a comic strip, but physics? No offense, I hope. I am just trying to do the math!
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Robert P
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PostPosted: Wed Aug 03, 2022 5:13 pm    Post subject: Reply with quote

abontrumpet wrote:

Robert P wrote:
Has anyone come up with a demonstration using maybe electronically actuated "lips" that more closely simulate the actions of human lips?

The demo in the video here shows sound can be made with a membrane without pushing air through but at no point does it match the tone of a normally played horn.


What would be the point of your demonstration, exactly? That the trumpet could be played like a trumpet? I'm not trying to be cheeky, genuinely don't understand.

I.e. mechanical "lips" where the buzzing is actuated electronically not by having air blown through them. This membrane demo shows an approximation of a trumpet sound but doesn't show that the sound can be the same without air flow.

Billy B wrote:

Listen at 6:20 in the video.

Meh - same as my reply above, still not the same.
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kalijah
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PostPosted: Fri Aug 05, 2022 4:38 am    Post subject: Reply with quote

Quote:
I.e. mechanical "lips" where the buzzing is actuated electronically not by having air blown through them.


That would not produce much sound. if any.

Actuated artificial lips WITH a supplied air pressure could produce a strong tone.
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JayKosta
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PostPosted: Fri Aug 05, 2022 5:13 am    Post subject: Reply with quote

Robert P wrote:

I.e. mechanical "lips" where the buzzing is actuated electronically not by having air blown through them. ...

--------------------------
If by 'mechanical lips' you mean moving surfaces that open and close, but do not 'pump air', then there wouldn't be much (if any) sound produced because the air pressure inside the tubing would not be changing.

Using a membrane transducer (or small speaker) will 'pump air' and produce the pressure changes that are needed.
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kalijah
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PostPosted: Fri Aug 05, 2022 7:47 am    Post subject: Reply with quote

Quote:
Using a membrane transducer (or small speaker) will 'pump air' and produce the pressure changes that are needed.


To have a speaker that could do equivalent sound levels of tone would require as significant power amplifier.

One issue with most speaker setups at that size feeding pure sine waves: The self-resonance of the speaker appears to affect the complete system response. This gives a broad "bump" around the Helmholtz resonance of the mp cup and even higher.
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Robert P
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PostPosted: Fri Aug 05, 2022 10:25 am    Post subject: Reply with quote

JayKosta wrote:
Robert P wrote:

I.e. mechanical "lips" where the buzzing is actuated electronically not by having air blown through them. ...

--------------------------
If by 'mechanical lips' you mean moving surfaces that open and close, but do not 'pump air', then there wouldn't be much (if any) sound produced because the air pressure inside the tubing would not be changing.

Using a membrane transducer (or small speaker) will 'pump air' and produce the pressure changes that are needed.

By mechanical lips I mean artificial lips that do the same thing human lips do but without air flowing through them. If it's true that the lips serve only to create the buzz and set up a wave in the existing air within the instrument, that no airflow is needed then they should work.
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Last edited by Robert P on Fri Aug 05, 2022 5:49 pm; edited 2 times in total
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john4860
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PostPosted: Fri Aug 05, 2022 12:31 pm    Post subject: Reply with quote

Re: Tom LeCompte

Apparently, he is the physics coordinator at CERN working on coordinating the large Hadron Collider science projects. He would get credit for papers he advised or helped with (I believe).

Pretty impressive stuff.

John
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