update.565 (fwd)

[Jim Choate]

---------- Forwarded message ----------
Date: Wed, 14 Nov 2001 15:53:42 -0500 (EST)
From: AIP listserver <physnews at aip.org>
To: physnews-mailing at aip.org
Subject: update.565


PHYSICS NEWS UPDATE                         
The American Institute of Physics Bulletin of Physics News
Number 565  November 14, 2001   by Phillip F. Schewe, Ben Stein, and
James Riordon

QUANTUM ACOUSTICS.   The flatland world of electrons
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SINGING LIKE A CANARY requires little thought, but simple
actions, to yield complex vocal physics, researchers have found,
yielding potential insights into how humans generate speech
sounds.  Human speech and the songs of many bird species share a
central similarity: the skills are not present at birth, but are only
learned through early-life experiences.  To determine how brain
activity leads to the production of sound, scientists strive to
understand how much of the sound comes from complicated
instructions from the brain and how much comes from complex
physics of vocal organs.  Now, a US-Argentina research
collaboration (Gabriel Mindlin, University of Buenos Aires,
Gabriel at birkhoff.df.uba.ar) has designed a simple physical model
that accurately reproduces notes of a canary song.  The researchers
modeled the canary's vocal organ, called the syrinx.  According to
previous experimental evidence, the syrinx generates sound
through vibrations of its labial "folds"---flaps of tissue which open
and close the air passage between the throat and the lungs.  In their
model, the researchers make the key assumption that these labial
folds behave like a simple spring, moving back and forth to change
the size of the air passage.  They further assume that a canary
controls its vocalizations through two actions: changing the
pressure of the air from the lungs and using muscles to modify the
stiffness of the folds. By varying these two parameters, the
researchers found that the spring-like labia could produce faithful
recreations of three canary notes.  Therefore, simple changes to a
basic system, rather than sophisticated instructions from the brain,
can reproduce the rich, complex vocal physics which give rise to
complicated sounds. (Gardner et al., Physical Review Letters, 12
November 2001)

THE FEMTOSECOND DELAY IN THE ADVENT OF collective
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