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Acoustic Zoetrope

April 9, 2010

Symmetry and Tiling
It is remarkable that even today we can fool the brain. Illusion is still possible. The Zoetrope was invented in the early 19th century, and after nearly two hundred years, persistence of vision still pleases us. In Living Art, Greg Borenstein and I spent some time studying persistence of hearing, and designed a geometric helmet that played a short soundpiece symmetrically around the listener’s head. You can see it here:

We hear the notes individually, but because the happen in sequence at a specific duration, our brain assembles them into a scale. Because they happen at different points in space, the scale takes on a spatial dimension, and melody appears to move through it.

Acoustic Zoetrope
For the midterm, I pursued the idea by enlarging the project to an entire room, and moving from chip-generated tones to recorded ones for more texture and depth.

The arrangement was simple, with six speaker points distributed at the four corners and centered on the long wall of Room 406 at ITP. They were all plugged into an M-Audio ProFire 610, and I played six mono tracks in Logic, varying their volume to demonstrate radial and bilateral acoustic symmetry. The sound effectively raced around the room faster and faster in the first example, and backwards and forwards in the second.

Mechanical Crank
My plan for my final is to introduce user interactivity into what is currently a passive experience. My initial plan was to utilize a found object, as there are many common household appliances with cranks. Here is a can opener I have for example that would work handily:

As the can rotates, the top remains stationary after it has been cut, and a simple rotary encoder affixed to it detecting the rotation can send a signal to a bank of solenoids by XBee radio, opeing and closing speaker circuits.

What I especially like about this idea, is that different cans can be set up with different sound patterns. A wide variety of off-the-shelf canned music.

I am also interested, though, in more physical demonstration and effort in the interaction. We use energy to conserve effort, and this makes sense, but it can also result in problems. Carpal Tunnel Syndrome, for instance, is a result of an over-reliance on micro-adjustment muscle groups in the wrists and hands, and under-reliance on macro muscle groups such as the back, shoulders and legs. Storytelling and dramatic effect are heightened as well by using more of the body in expression, and perhaps pursuing a less efficient course of action. And the can opener does not really encourage multi-player participation, but rather a performance with an audience.

I got to thinking about the mechanism of the handcar: it also uses a lever to generate rotary motion, but while it can be operated by a person alone, it typically takes two people to power it in a journey down a track:

[Courtright Manufacturing Co., of Detroit]
Building this as a bicycle would be hilarious, but I think it would have all the disadvantages of a train and none of a bike. My plan is to build a stationary version that would turn one wheel above the floor, serving as a rotary encoder.

I am in the process of drawing this up, but here is a basic materials list:

Platform (foot rests), tower, crank brace and handle: wood
Gear and chain drive: repurposed bicycle
Rotary encoder wheel: probably bicycle wheel, but TBD
(4) Steel rods, smooth with threaded ends
Carriage bolts and bushings

I’m not certain yet about the chain drive as it’s obviously a bit redundant–the wheel could be simply attached to the central axle–but I like the idea of building momentum, and a flywheel would be necessary for that.


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