Re: [time-nuts] Helmholtz Resonator and other Maintained Oscillators

[Magnus Danielson]

Hi,

Recommended reading relating to this is the acoustical and audio 
engineering material.


"Acoustical Engineering" by Harry F. Olson is a really good book. I 
covers many of the theory work on speakers etc. and uses electrical 
models and ways to estimtate their effects. This book I have used to 
again and again debunk "new" speaker concepts, as it turns out it has 
already been tried before.


AES have released 4 collections of articles out of JAES on speakers. In 
there is the moderload of Thiele-Small articles that extends the work of 
Olson to more and more refined methods. Estimating the losses and 
resonant properties is a key aspect, as they have huge impact on the on 
the audio.


Also, there is a good book on acoustics by Beranek, of 
Bolt-Beranek-Newman if that rings a bell to Internet old-timers, which 
may be applicable.


I could do a more detailed dig in my library if needed, but there is 
some good material out there.


Cheers,
Magnus - AES member and used to do professional audio PA system design

On 12/10/2017 01:30 AM, Bill Byrom wrote:

The Q of Helmholtz resonators is derived here:
https://en.wikibooks.org/wiki/Acoustics/Flow-induced_Oscillations_of_a_Helmholtz_Resonator

Some Q measurements of bottles are described here:
https://math.dartmouth.edu/archive/m5f10/public_html/proj/ArainGolvach.pdf

--
Bill Byrom N5BB

On Sat, Dec 9, 2017, at 01:39 AM, Hal Murray wrote:


k8yumdoo...@gmail.com said:

The flex hose demonstration was interesting in that different regimes of
swinging speed resulted in oscillation in different modes.  I wonder why.


It depends on the speed of the air going through the tube.

https://www.youtube.com/watch?v=4aJ36-TlPD4

http://www.exo.net/~pauld/activities/AAAS/aaas2001.html
http://www.exo.net/~pauld/summer_institute/summer_day13music/Whirly.html


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Re: [time-nuts] Helmholtz Resonator and other Maintained Oscillators

[Ulrich Rohde via time-nuts]

 
This is a very nice technical discussion ...
 
Ulrich
 
 
In a message dated 12/9/2017 7:31:15 PM Eastern Standard Time, 
t...@radio.sent.com writes:

 
 The Q of Helmholtz resonators is derived here:
https://en.wikibooks.org/wiki/Acoustics/Flow-induced_Oscillations_of_a_Helmholtz_Resonator

Some Q measurements of bottles are described here:
https://math.dartmouth.edu/archive/m5f10/public_html/proj/ArainGolvach.pdf

--
Bill Byrom N5BB

On Sat, Dec 9, 2017, at 01:39 AM, Hal Murray wrote:
> 
> k8yumdoo...@gmail.com said:
> > The flex hose demonstration was interesting in that different regimes of
> > swinging speed resulted in oscillation in different modes. I wonder why.
> 
> It depends on the speed of the air going through the tube.
> 
> https://www.youtube.com/watch?v=4aJ36-TlPD4
> 
> http://www.exo.net/~pauld/activities/AAAS/aaas2001.html
> http://www.exo.net/~pauld/summer_institute/summer_day13music/Whirly.html
> 
> 
> -- 
> These are my opinions. I hate spam.
> 
> 
> 
> ___
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Re: [time-nuts] Helmholtz Resonator and other Maintained Oscillators

[Bill Byrom]

The Q of Helmholtz resonators is derived here:
https://en.wikibooks.org/wiki/Acoustics/Flow-induced_Oscillations_of_a_Helmholtz_Resonator

Some Q measurements of bottles are described here:
https://math.dartmouth.edu/archive/m5f10/public_html/proj/ArainGolvach.pdf

--
Bill Byrom N5BB

On Sat, Dec 9, 2017, at 01:39 AM, Hal Murray wrote:
> 
> k8yumdoo...@gmail.com said:
> > The flex hose demonstration was interesting in that different regimes of
> > swinging speed resulted in oscillation in different modes.  I wonder why.
> 
> It depends on the speed of the air going through the tube.
> 
> https://www.youtube.com/watch?v=4aJ36-TlPD4
> 
> http://www.exo.net/~pauld/activities/AAAS/aaas2001.html
> http://www.exo.net/~pauld/summer_institute/summer_day13music/Whirly.html
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
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Re: [time-nuts] Helmholtz Resonator and other Maintained Oscillators

[Hal Murray]

k8yumdoo...@gmail.com said:
> The flex hose demonstration was interesting in that different regimes of
> swinging speed resulted in oscillation in different modes.  I wonder why.

It depends on the speed of the air going through the tube.

https://www.youtube.com/watch?v=4aJ36-TlPD4

http://www.exo.net/~pauld/activities/AAAS/aaas2001.html
http://www.exo.net/~pauld/summer_institute/summer_day13music/Whirly.html


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Re: [time-nuts] Helmholtz Resonator and other Maintained Oscillators

[Dana Whitlow]

Use of a smaller opening would be the first strategy for getting higher Q.
Making sure that the walls of the vessel were solid reflectors would be
an important factor, too.

I noted that several of his sustained oscillators were basically either
relaxation or blocking oscillators, neither of which is noted for good
phase noise performance.  Even the pendulum clock mechanism
was interfering severely with the pendulum's motion- if you look
closely you can see that the pendulum bob's position versus time
function was a severely clipped waveform.

The flex hose demonstration was interesting in that different regimes
of swinging speed resulted in oscillation in different modes.  I wonder
why.  But in hearing people learning to play different musical instruments,
mostly wind instruments but also including the violin, I was once
moved to say that playing these devices the art was in making an
oscillator run in a resonator mode other than the "natural" one.

For an  interesting look at oscillating modes and a really oddball
sustained oscillator, view  https://www.youtube.com/watch?v=m6631u7d4E0.
and/or google "mercury beating heart".  The electrochemical effect
makes the blob oscillate between a hunched-up shape and a flattened
shape.

If given time, this hunching oscillation "pumps" a degenerate parametric
oscillation between the two triangular shapes at nominally half the rate
of the original oscillation.  I first saw this demonstrated in high school,
but the demonstrator also could  not get a sustained oscillation.  I
thought about that for a while and decided to try a little external stimulus
in the form of low voltage DC from an external supply.  After a little
optimization it worked beautifully and could run for hours on end with
little of no attention, giving me the luxury of trying a range of different
blob sizes.  With different sizes I could get sustained parametric
oscillation in four different modes: 2-sided, 3-sided (as seen in the
You-Tube clip), 4-sided, and with difficulty even 5-sided.

Of course I didn't really understand what was going on at the time,
and didn't arrive at the parametric oscillation theory until years later.
BTW, I used a baking soda solution instead of a chromium-based
chemistry, and an electrode coming down from the top center, with
a large ring surrounding the mercury blob as the other electrical
connection.

Solution concentration, voltage, electrode tip height, and electrical
polarity were the parameters that had to be adjusted for best
performance.  A mercury blob about one cm across in its resting
state seemed to be a good starting point.  For polarity, use the
one that results in the blob's hunching up when the electrode tip is
gradually lowered into contact with the blob.  If the other stuff
is not too far off, it will quickly take off oscillating at that point.

I've been wondering whether this could be made to work with
Galinstan obtained from modern-day clinical thermometers,
instead of that dreaded mercury.  A worthwhile experiment
to try.

I never did get around to measuring the Alan Variance of one
of these oscillators; indeed, I didn't even hear of the concept
until years later.  It's probably not up to Time-Nuts' standards.

Dana

On Fri, Dec 8, 2017 at 4:59 AM, Hal Murray  wrote:

> What's the Q of a Helmholtz Resonator?  What do I do to make a high(er) Q
> version?
>
> With a narrow band filter, it might make a neat demo/toy to pull an audio
> signal out of the noise.  With 2 at different frequencies you could
> demonstrate FSK.
>
> --
> These are my opinions.  I hate spam.
>
>
>
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Re: [time-nuts] Helmholtz Resonator and other Maintained Oscillators

[Hal Murray]

What's the Q of a Helmholtz Resonator?  What do I do to make a high(er) Q 
version?

With a narrow band filter, it might make a neat demo/toy to pull an audio 
signal out of the noise.  With 2 at different frequencies you could demonstrate 
FSK.

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Re: [time-nuts] Helmholtz Resonator and other Maintained, Oscillators

[Dr. Ulrich L. Rohde via time-nuts]

Top presentation! 73 de Ulrich

Sent from my iPhone

> On Dec 6, 2017, at 1:47 PM, Joe Leikhim  wrote:
> 
> Great stuff. Helps understand Magnetrons, Injection locking, etc. Also love 
> those relaxation oscillators.
> 
> -- 
> Joe Leikhim
> 
> 
> Leikhim and Associates
> 
> Communications Consultants
> 
> Oviedo, Florida
> 
> jleik...@leikhim.com
> 
> 407-982-0446
> 
> WWW.LEIKHIM.COM
> 
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Re: [time-nuts] Helmholtz Resonator and other Maintained, Oscillators

[Joe Leikhim]

Great stuff. Helps understand Magnetrons, Injection locking, etc. Also 
love those relaxation oscillators.


--
Joe Leikhim


Leikhim and Associates

Communications Consultants

Oviedo, Florida

jleik...@leikhim.com

407-982-0446

WWW.LEIKHIM.COM

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[time-nuts] Helmholtz Resonator and other Maintained Oscillators

[Brooke Clarke]

Hi:

I'm watching this hour lecture on YouTube by the Naval Postgraduate School (NPS) for information about Helmholtz 
Resonators, but recommend it here because there's excellent demonstrations of time related ideas.

Helmholtz Resonator and other Maintained Oscillators
https://youtu.be/y86QhzesYok

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

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