1. Forum
  2. Usenet
  3. COMP.SYS.AMIGA.HARDWARE

  • Weird Behavior: French Horn + Monitor

    From boeing377@gmail.com@21:1/5 to Bob Dickow on Thu Jan 26 14:39:04 2017
    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

    On Monday, October 3, 1994 at 1:08:15 AM UTC-7, Bob Dickow 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.

    --

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

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From MoJoe44@21:4/137 to boeing377@gmail.com on Thu Oct 22 02:26:43 2020
    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.

    --- Mystic BBS v1.12 A46 2020/03/02 (Windows/32)
    * Origin: 8-Bit Boyz BBS! -=[ bbs.8bitboyz.com port:6502 ]=- (21:4/137)
  • From MoJoe44@21:1/5 to All on Thu Oct 22 02:26:42 2020
    From: MoJoe44@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.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)