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Perturbation is an interactive installation that uses a speaker hanging as a pendulum from the ceiling surrounded by a hexaphonic speaker setup to create a responsive sound environment. Besides being a sound source, the pendulum speaker is also the interface by which the audience interacts with the installation. Through pushing, pulling and twisting, the audience can move the pendulum and set it into oscillating motions. Sensors inside the pendulum continuously track its position, orientation, acceleration and speed. These data are processed and used to react to the pendulum’s motions by means of sound. The surrounding speakers also react to the pendulum as it approaches them, resulting in a responsive and real-time generated sound environment.​

For the design of the audience interaction, we make use of the pendulum speaker’s physical swinging behaviour. We have developed an algorithm that predicts the pendulum’s natural swinging movement and detects perturbations in this movement caused by the audience pushing, pulling and rotating the speaker. This allows the installation to detect and react directly to the audience’s actions. The way in which the installation reacts to the audience is controlled by a system of rules inspired by mathematical models used to model the dynamics of biological populations. This system enables the behavior of the installation to evolve as a result of the amount of energy that the audience puts into it. By this, the audience can bring the installation into different ‘states’ that each have their own sounds and rules for the interaction.


At first, it may seem that the audience can control the installation’s behavior predictably. However, perturbing the pendulum's natural swinging motions too much causes the installation to spiral into chaotic and unpredictable behavior. This, combined with the fact that hard physical labour is needed to restrain the pendulum, leads to a tense dialogue between participant and object, struggling for control. The movements resulting from this dialogue cause the sounds in the environment to change between different states of stability and chaos, hereby mirroring the types of dynamics that are also seen in natural ecosystems.

Exhibited at NIME 2018

Paper about the work won Best Paper Award at ArtsIT, Interactivity & Game Creation 2018

Concept and realization: Jelger Kroese, Danyi Liu and Edwin van der Heide

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