Sustainable: a dynamic robotic sound installation

by David Birchfield, David Lorig, Kelly Phillips

2004

Sustainable is comprised of a network of robot water gongs that are linked together by water tubes that allow each tank to receive water from one upstream neighbor, and to pump water into one downstream neighbor. The network is a closed system that distributes water between the members.

Sustainable video with voiceover overview (requires quicktime player)
Short videos - please click images below to play video documentation of the installation (requires quicktime player)

We are inspired by the current water resource crisis in the western US states, and have implemented a water resource sharing algorithm that is used to negotiate multiple consumer demands against the available water supply. Imagine that the system is like as a group of farmers or golf courses that have high demands for water usage, but must share and negotiate for the rights to use water.

Each water gong node has a fluctuating water demand need that is periodically updated - just as farmers will need varying amounts of water as the seasons turn. By turning its water pump on or off, a given water gong can either conserve or purge water so that the amount in its tank will match its need. In this respect, each node is functioning selfishly and independently. However, given that the network only has a finite amount of water, the system as a whole is in constant flux as water is distributed around the network and the system itself attempts to achieve equilibrium. The individual nodes use simple, deterministic rules to govern their behavior, but the network as a whole demonstrates non-linear, emergent behavior.

As the amount of water in a given tank dampens the gong, the pitch of the gong will rise and fall. Therefore, in addition to seeing the water resource as it is distributed and redistributed around the system, viewers can hear the ever-changing state of the system, and see the reflection of rippling water on the ceiling.

What are the ideas?

Water is an important conceptual and metaphorical force in this piece. It serves as the means of communication between nodes in the network, and this anachronistic mechanism references the use of waterways as the traditional vehicle for communication and transportation. The network of water gongs share a limited resource of water, and its constantly shifting allocation between the members of the system models the shifts of natural, cultural, and intellectual resources throughout the networks of our local and global communities. The sonic and visual aspects of the piece represent the states and shifts of the network as it passes through moments of stability and instability.

An important design principle for the work is that the technology should be downplayed rather than fetishized. This concept informs the decision to have the sound and sonic events originate from 'natural' and not electronic sources. Similarly, the technology is present only in the background of the piece thus allowing the audience to focus on the organic aspects of the work.

How does it work?

Each water gong node has several components:

1. a gong
2. 7-element float switch mechanism to sense the current water level
3. two solenoid beaters
4. a submersible water pump
5. embedded bottom-illumination light
6. custom microprocessor and control circuitry

A set of simple behaviors govern the actions of each autonomous gong. Depending on the amount of water in the tank, and a gong's desired water level, each gong will independently iterate through these steps:

1. updating water consumption need
   each gong node selfishly attempts to have its water level match its water demand. Each gong cyclically updates its desired water level after a specified number of actions. This behavior is analogous to the way in which actual water consumers will have different needs as seasons change and time progresses.
2. water pumping
   If the current water level in a gong's tank exceeds its need, it will turn its water pump on to purge water. If the current level is below its need, it will keep its pump off in order to conserve water. However, its water level will only increase in this situation if its upstream neighbor simultaneously purges water.
3. striking the gong
   There are 4 modes of gong striking: silence, sporadic single strikes, alternating strikes at a constant rate, and alternating strikes with accelerating/decelerating motion. Each gong node will move through and hold these striking states according to the proximity of the current water level to the desired level.

4. illumination
   The lamp below the gong is illuminated when the current water level does not meet the desired level. Depending on the state of the gong strikes, the lamp illuminates ripples in the water that result from the gong's reverberation. The character of this visual element depends on the amount of water in the tank, the size and type of gong, and the mode of beating. In a darkened exhibition space, the illumination will project onto the ceiling, thus providing a meta-display of the activity of the network.

We are grateful to the Arts, Media and Engineering program at Arizona State University for its support and encouragement that made this work possible. Also, many thanks to Assegid Kidané for his invaluable advice, troubleshooting and enthusiasm.

more installation documentation