Weird Behavior: French Horn + Monitor

[b***@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

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.
--

[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: ***@f137.n4.z21.fsxnet (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.