Weird Behavior: French Horn + Monitor

[Bob Dickow]

This question could go to any hardware/monitor/physics/accoustics
newsgroup, I suppose...

Sometimes while playing certain notes on my French horn in the
same room with a running video monitor or TV, I can set the
display into a vibratory ripple, or sort of wavy distortion.

My question is, why would sound waves affect the video display
so? My hypothesis is that maybe the whole cathode ray tube is
going into syphathetic vibration/resonance, but the effect seems
rather dramatic.

--

--Bob Dickow (dic...@crow.csrv.uidaho.edu)

[Gary Bates]

Bob Dickow (dic...@raven.csrv.uidaho.edu) wrote:
: This question could go to any hardware/monitor/physics/accoustics
: newsgroup, I suppose...

I think it's you not the TV....have you got anyone else to watch whilst you
play the horn? Strange things *can* happen....the same sort of thing
happens to our TV when I eat my cornflakes in the morning! :)

--
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[Brian Kokernak]

Try clearing your throat. This works the best me thinks, and you can
usually keep it up for a while with practice.

(I'm a little bored with my Amiga lately.)

Brian Kokernak
bria...@delphi.com

[Jamuel Starkey]

In article <941004130...@batesg.demon.co.uk>,

Me too! If you are crunching on ice or if you yell real loud at the screen...

JPS

[Andrew Clayton]

That's YOUR EYES are are reporting a problem, not the TV actually doing
something weird.

You can get the same effect if you blow through your lips and make a
humming sounds. An easier way to see weird effects is to wave your hand,
with fingers splayed out, palm flat to the CRT, at about 2
cycles/second.

Depends upon the scan rate of your monitor.

For verification, get someone _else_ to play the french horn, and you'll
never see anything change, no matter what note is played.

Dac
David Andrew Clayton.
Canberra, Australia.
d...@prolix.apana.org.au
A Caring Prolix Bastard.

[Jamie Krutz]

In article <941004130...@batesg.demon.co.uk> ga...@batesg.demon.co.uk (Gary Bates) writes:
> Bob Dickow (dic...@raven.csrv.uidaho.edu) wrote:
> : This question could go to any hardware/monitor/physics/accoustics
> : newsgroup, I suppose...
>
> : Sometimes while playing certain notes on my French horn in the
> : same room with a running video monitor or TV, I can set the
> : display into a vibratory ripple, or sort of wavy distortion.
>
> : My question is, why would sound waves affect the video display
> : so? My hypothesis is that maybe the whole cathode ray tube is
> : going into syphathetic vibration/resonance, but the effect seems
> : rather dramatic.
>

Do you wear glasses? Might be vibrating your glasses...

Best,
-Jamie

[Jeff Walkup]

!!!

Try this: stand back about 10 feet (3 meters) from your monitor,
stick your tounge out and do a "raspberry", that is, PPPTTTTTHH...
(hmm, kind of hard to describe...)

Does the monitor's image vibrate or "wiggle"? I think this is what's
happening. In other words, your head is vibrating.

!!!!

--
Jeff Walkup . jwa...@crl.com . San Francisco . 415.668.7312

[Daniel Barrett]

In article <36oe5f$t...@owl.csrv.uidaho.edu>,

Bob Dickow <dic...@raven.csrv.uidaho.edu> wrote:
>Sometimes while playing certain notes on my French horn in the
>same room with a running video monitor or TV, I can set the
>display into a vibratory ripple, or sort of wavy distortion.
>My question is, why would sound waves affect the video display
>so?

Bob, just press Ctrl-Alt-LeftAmiga-Shift-B and pop up the
memory-resident copy of BLAZEMONGER XXIV that is apparently running in the
background. BLAZEMONGER hates the sound of French horn and is visibly
shuddering when you play it. To eliminate the problem, try playing electric
guitar instead, or perhaps a lute cranked through a distorted amplifier.

Dan

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| Dan Barrett -- Computer Science Dept, University of MA, Amherst, MA 01003 |
| http://zoo.cs.umass.edu/~barrett/public.html -- bar...@cs.umass.edu |
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[boei...@gmail.com]

I used to play second chair French horn with Bob in high school. The talent gap between first and second chair was IMMENSE, which is why I got a BSEE at UC Berkeley and Bob went on to get his PhD in music. I can't rule out the physio explanations but it's possible that there are components in the monitors that are exhibiting microphonic behavior. It's common in vacuum tubes (CRT is a vacuum tube) but it occurs occasionally in all sorts of other components, both passive and active. The acoustic forces cause a change in an electrical property of a component and in turn the behavior of a circuit. The change is often proportional to the amplitude and sometimes frequency of the acoustic wave that impacts the affected component.
See: https://en.wikipedia.org/wiki/Microphonics.

Mark Meltzer
Palo Alto CA

[MoJoe44]

Not surprising as a HAM radio operator microphonic sound can occur in Capcitors
Circuit Boards, Transistors and of course Vacuum tubes is well known.
Feedback in the shack can also occur from high voltages from the RF.
Windows made of silica also exhibit microphonic sound qualities. Just about any
surface can reflect sound waves and be subject to amplification. There are
agencies that utilize this effect to evesdrop in on American Citizens without
the need for a wiretap writ. I suggest humming offkey frequencies to disrupt
the environment that the listener is using. A rounded foil hat will disperse
micorwaves used for cerebral penetration. A Conical foil hat will actually
amplify the signal, people will tend to think you are crazed and shows
little fashion design thought.

[MoJoe44]

From: MoJ...@f137.n4.z21.fsxnet (MoJoe44)