Klarinet Archive - Posting 000252.txt from 2000/02

From: "M. W. Presson" <docbones@-----.net>
Subj: Re: [kl] re:That thing is *huge*!
Date: Sat, 5 Feb 2000 16:53:44 -0500

> > I too am a southpaw and proud of it. As for huge, tubas and contrabass
> > clarinets are neck and neck. However I never met a tuba player whose
> > playing made his or her eyes rattle. I HAVE heard of contrabass players
> > having this happen!

Along with my experiences on Bass and Contra clarinets, I play the tuba from
time to time--It rattles one's eyesight there, as well. Many a time have I
been playing a basketball pep band gig on tuba, and looked up at the
scoreboard while playing.

The interesting part, however, is not that the vibrations occur, but that
they seem to only affect things that are glowing. Well, using what I know
of physics, my explanation is thus: Our brain is very much used to seeing
things move around, i.e. when we walk, our field of vision is constantly
changing. So it knows how to compensate, and at any given instant, we get a
composite of what is actually there, and what is assumed to be there, based
on what was visible moments before.

But lighted objects are particularly strange. They carry a stark contrast
to their immediate surroundings, and by glowing, are a little harder to
focus on. Especially the edges of a computer screen and LED displays. They
are also constantly fading and being re-lit. So what you see on the
scoreboard in front of you is your brain's composite of a lit diode and an
unlit diode. As the lit diodes are so much more stark to their
surroundings, you get a series of pictures, about 60 times a second, instead
of a constant flickering. Until you start playing a low note on your
contrabass clarinet or tuba. The fundamental, and some of the overtones do
indeed vibrate your eyes. The instrument's frequencies create beats with
the refresh rate, or frequency that the diode is given a current. Thus you
get different frequencies of apparent flickering, due to the different rates
of interference...

Your eyes, although they are not quick enough to compensate to the
vibrations relative to the lighted diodes, are quick enough to make a
composite of the easier-focusing, and non oscillating flat surfaces. That's
why the lighted computer screen and scoreboard numbers seem to vibrate
against the stationary backgrounds.

- Matt

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