Re: making sound waves visible

[William Beaty <billb@ESKIMO.COM>]

On Mon, 13 Sep 1999, Herbert H Gottlieb wrote:

> William...
>
>
> Why don't you photograph the studetns as they flap their arms. This,
> together with a short explanation would make a terrific cover story for
> The Physics Teacher magazine.


No access to any students at present.  (I'm a grunt programmer in a laser
barcode company.)

Hmmmm.  Just a person with a cardboard megaphone would be enough.  Yell
"up-down-up-down-up-down!" at a brisk pace, like five changes per second,
and a photographer up in the bleachers at the ballfield would have a great
photo-op.  A 2.5 Hz wave would make a complete cycle in 440 feet, so maybe
we'd want to use little kids (less moment in their arms) and set a really
frenetic pace of arm-flapping (shorter wavelength).  If they close their
eyes and just listen to the megaphone, they might produce a really nice
sinusoid.

This idea would be great at a sports arena.  Have everyone standing up,
then use a single loudspeaker and say "everyone sit down instantly when I
hit zero:  five four three two one zero!"  The visible sound wave might be
pretty impressive.  But the mechanical transient of all those butts
hitting the seats within a fraction of a second might reduce the stadium
to rubble.  Just like the propagating the overpressure from a nuke or a
fuel-air bomb!  "Sports Arena Destroyed During "Synchronized Sitting"
Experiment, Hundreds Die."  We wouldn't even need the population of Los
Angeles to simultaneously leap from a 1-meter ladder!  :)


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William J. Beaty                                  SCIENCE HOBBYIST website
billb@eskimo.com                                  http://www.amasci.com
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