h a l f b a k e r yWhat was the question again?
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Girderphonic
a ten storey building containing a single hanging girder | |
In a ten storey building a single metal girder freely
hangs, which
extends into a space below the ground floor. In this
underground
space, the girder is surrounded by water, the level of
which can be
quickly altered by rapid action hydraulics. These
hydraulics are
controlled by a piano
style reduced keyboard contained
in a separate
room. You may have figured out by now that this is the
descriptor for
a new analogue sound instrument.
Here's how it works: one person equipped with ear
defenders
delivers a single hammer blow to the girder, causing it to
emit a
massive vibration. This vibration is then attenuated by
the rising and
falling on the water, as the second operator controls the
sound using
the previously described keyboard. A row of identical
towers would
enable orchestrated sounds to be generated.
I have no idea if this would actually 'work', but that's why
it's resting
here in the halfbakery, as the construction crew lean on
their shovels.
Stomp Out Loud
https://www.youtube...watch?v=fN5T8y8bCJ4
I dunno about girders, but it works quite well with what appear to be scaff poles. (~18 minutes in.) [Wrongfellow, Mar 04 2016]
[link]
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The pumps would be noisy. Would it be better to have rubber attenuators? |
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The pumps would be soundproofed. |
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I don't think the water is going to do what you want
it to do. At best, it is going to partially damp* the
sound (acting at one end of the girder), and change
the resonant frequency only a little. |
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(*Although this may appear to be a pun, it is, in
actual fact, not.) |
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The water sloshing in and out of the pumps is what will be noisy, not the mechanical action of said pumpacious devices. |
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Max - a small change will suffice. Perhaps some method of
rapidly varying the viscosity would be good, but not easily
achieved except in a one way, non reversible direction ie
thixotropic substances? |
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But again, you will only be damping the vibrations -
their pitch will not change as much. So, you may get
some pitch variation, but the higher notes will be
duller. |
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This might work if, instead of a liquid, you used a
semi-solid and raised or lowered the girder into it. I
think a few hundred tons of foie gras would have the
right sort of consistency, |
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Liquefied carnivores it is then. They can keep their clothes on as they pushed and prodded along the sterile corridor towards the Soylent Green blender! ha |
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I'm a vegetarian, but I eat meat as well. No point
being faddy, I always think. |
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An excellent find [Wrongfellow] though obviously on a much smaller scale and a reversal of the idea that it's the water level that changes, but it does prove that the idea would work. I would love to build it. More failed grant applications on the way then! |
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Of course, one major difference between a girder and a pole is the presence of a resonant column of air in the interior of a pole. |
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//a few hundred tons of foie gras// |
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Using mercury instead might enhance the desired "impedance mismatch" effect while also showing less undesirable damping. |
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Unfortunately, combining foie gras with mercury is far beyond my meagre culinary skills. |
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I love the proposal to work around cumbersome, fussy pumps by varying fluid viscosity. And the idea of changing the water level rather than raising and lowering the girder. Tom Sawyer would approve! |
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But Max thinks the water will not work. I think it might. It is easy to take a pencil, or a butter knife, pr preferably 2 butter knives and tap while changing the free length - the pitch changes. Would water dampen as well as fingers? |
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I can very much imagine the girder as sculpture, hanging in the open lobby of a skyscraper. The Chime of Damocles. But implementing this whole idea would get people wet. Plus the water would gush out into the street when people opened the doors. How to change the pitch of a hanging piece of metal? |
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// Would water dampen as well as fingers? // |
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Water dampens a lot better than fingers, unless the fingers
are bleeding or have been dampened themselves. Now, does
water *damp* as well as fingers? That I don't know. |
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