More aeolian
AlCarruth@aol.com
Wed, 5 Jun 1996 08:39:34 -0400
The whole aeolian effect is really interesting. I saw an animation a few
months ago of a computer model of airflow past a cylinder and the eddies
breaking off on the downstream side were beautiful, first above and then
below the cylinder.
The window instrument my friend made looks more like a psaltry than a
harp. It is a rectangular box the same length as the windowsill with the
strings stretched along the top. The top is actually set at an angle, when
seen from the end, so that the side toward the window is lower than the side
toward the room. There is a cover for the top, and this forms a tapered slot
which, in theory, should speed up the airflow as it goes from the window
toward the room, thus ensuring that there will be some region where the flow
will be fast enough to trigger the singing. In practice, this one works
better without the cover. It has a dozen or so steel strings, all the same
length, which he tunes to chords (C-E-G over and over, for example). It seems
to work best, with such short strings, to leave them fairly slack. It is true
that metal strings are harder to get going in the wind because they have more
mass and less drag than nylon. Some people use strings of different materials
all tuned to the same pitch. They tend to have slightly different overtones,
and it is the overtones that get activated.
He tried making one last summer out of a hollow-core door, but it didn't
work out.
At least some of the outdoor ones I have heard of use stainless steel
wire. Nylon would tend to break down when exposed to ultraviolet, and other
metals corrode. If you made one with a cover to protect the strings from the
weather it would probably have to be screened to avoid becoming a wasp nest.
Some people find the music 'weird' or 'eerie', but I find it soothing;
the aural equivalent of watching a fire. It is much more various than wind
chimes, and more in tune with the environment; low and quiet when the breeze
is gentle, and higher and louder as the wind rises. I often think that
someone could sell a bunch of these through yuppie catalogs if they could
work out the design and production. As I say, another project on the Endless
List.