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Date: Mon, 15 Nov 1999 20:18:58 -0500
From: jim and joyce <lande@erols.com>
Subject: the shakes
Reply-To: contrabass@contrabass.com>>My contrabass clarinet's lower notes make the computer
>>screen shake and pulsate. Why?>Resonance.
Grant, I think you are half right. First, let me observe that it takes
an odd sort of person the sit and play a contra clarinet and read e-mail
and search eBay at the same time. When I was doing this, I noticed the
screen getting wavy -- almost like moray patterns. I asked my wife &
kids and they didn't see anything unusual on the screen. They also
couldn't see my head vibrating (although they do wonder if my head won't
explode when I play the fool thing, and they all keep their distance,
just in case.) I think that the vibrations of the instrument make my
eyeballs vibrate at some multiple of the screen scan rate, enough so
that more than one line appears at some points on my retena and none at
others. This is sort of like resonance. Of course, I am an economist
and all sorts of strange theories seem reasonable to me, so it would be
better if a real science type weighs in on this. After all, maybe my
family lied ot me in the hopes that I would give up the beast to save
the computer..jim lande
---------------------------------------------------------
Date: Mon, 15 Nov 1999 20:22:15 -0500
From: jim and joyce <lande@erols.com>
Subject: and also
Reply-To: contrabass@contrabass.com>>When I was in high school, my bari sax practicing used to
>>cause our TV screen to blur, much to my sisters' annoyance.Grant, is it possible that your TV had tubes? I wonder if vibrations
would effect a tube model more than the current solid state things.---------------------------------------------------------
From: "J. Daniel Ashton" <jdashton@bellsouth.net>
Date: Mon, 15 Nov 1999 22:23:37 -0500
Subject: Re: and also
Reply-To: contrabass@contrabass.com>>>>>> "jaj" == jim and joyce wrote:
jaj> Grant, is it possible that your TV had tubes? I wonder if
jaj> vibrations would effect a tube model more than the current solid
jaj> state things.Now I have to throw this in. I was at rehearsal for Zephyr Brass Choir
(anyone else in Atlanta?) playing tuba, and saw a very significant
shake on a cheap computer monitor across the room. I have a number of
witnesses who stopped playing to observe the phenomenon.Point being, it's not just the eye sockets of the tuba (or contra)
player - others in the group observed it too.I spent a fair amount of time this afternoon practicing BBb
contra-bass in close proximity to my computers, listening for an
incoming message. (Shostakovich' Festive Overture - man, what a rush!)
However, I kept my back turned to the monitors, so I don't know whether
they were shaken.--
mailto:jdashton@southern.edu J. Daniel Ashton ICQ# 9445142
mailto:jdashton@us.ibm.com http://www.southern.edu/~jdashton
mailto:jdashton@bellsouth.net <-- NeXTMail PGP key available
---------------------------------------------------------From: Fmmck@aol.com
Date: Mon, 15 Nov 1999 23:39:26 EST
Subject: Re: the shakes
Reply-To: contrabass@contrabass.comIn a message dated 11/15/99 8:17:57 PM, lande@erols.com writes:
<< >>My contrabass clarinet's lower notes make the computer
>>screen shake and pulsate. Why?>Resonance.
Grant, I think you are half right. First, let me observe that it takes
an odd sort of person the sit and play a contra clarinet and read e-mail
and search eBay at the same time. When I was doing this, I noticed the
screen getting wavy -- almost like moray patterns. I asked my wife &
kids and they didn't see anything unusual on the screen. >>Jim-
This is due to a stroboscopic effect. In other words, the screen is sort-of
flashing (being scanned) at a low rate, in the range of 30 to 75 times per
second. Normally your eye sees it as continuous, but if the vibration is
synchronized with the scan rate or a multiple of it, then your vision may
perceive it as shaking or pulsating.Fred McKenzie
---------------------------------------------------------Date: Tue, 16 Nov 1999 08:11:20 +0000
From: David Bobroff <bobroff@CENTRUM.IS>
Subject: more shaking screen
Reply-To: contrabass@contrabass.comAdam Kent-Isaac asked:
>My contrabass clarinet's lower notes make the computer
>screen shake and pulsate. Why?And Grant Green said:
>Resonance. Your computer screen apparently resonates at a frequency
>near the contra's lower range. If you play loud enough, the screen
>shakes. There are probably a number of things in the area that shake
>too, its just that it is easier to notice when the computer screen
>shakes due to the image blurring. Other resonances are generally not
>noticed unless something rattles or buzzes.
>
>When I was in high school, my bari sax practicing used to cause our
>TV screen to blur, much to my sisters' annoyance. Is it any wonder I
>practiced so much?... ;-)This is the first time I have ever heard of anyone besides the one playing
the low note being able to see the shaking screen effect. As far as I
knew, the effect was caused by the difference between the refresh rate of
the screen and the note being played. When you play wind instrument your
skull vibrates too. If this gets close to the refresh rate of the screen
you start to get this effect.David Bobroff
---------------------------------------------------------Date: Tue, 16 Nov 1999 10:55:28 -0700
From: Grant Green <gdgreen@contrabass.com>
Subject: Re: more shaking screen
Reply-To: contrabass@contrabass.com
>
>This is the first time I have ever heard of anyone besides the one playing
>the low note being able to see the shaking screen effect. As far as I
>knew, the effect was caused by the difference between the refresh rate of
>the screen and the note being played. When you play wind instrument your
>skull vibrates too. If this gets close to the refresh rate of the screen
>you start to get this effect.Unable to resist complicating matters further, I have to mention that
I notice a similar effect *on sheet music* when playing contrabass
clarinet fortissimo - as long as I'm wearing glasses at the time...Grant
+++++++++++++++++++++++++++++++++++++++++++++
Grant Green gdgreen@contrabass.com
http://www.contrabass.com
+++++++++++++++++++++++++++++++++++++++++
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