Luc Döbereiner

Interior/Exterior (2012)
sound installation

Interior/Exterior was presented at the exhibition space ESC in Graz, Austria, in January 2012. The installation consists of, on the one hand, a physical set-up consisting of a metal sheet (a roof tile), six loudspeakers, and four microphones, and, on the other hand, a physical modelling sound synthesis program. The metal sheet resonates, it responds non-linearly and differently depending on the location of the excitation - that is, the placement of the loudspeakers. There are six loudspeakers facing upwards under the plate and four loudspeakers (used as microphones) facing downwards on top of the plate (see image). The sound output hence excites a body at different places, while the loudspeakers scan its resonances and feed the resulting signal back into the software synthesis model. The metal sheet thus acts as a vibrating speaker membrane, projecting the sound upwards.

The synthesis method itself is based on the idea of a circle of connected springs and masses that are being displaced by input signals (recorded by the microphones) and stochastic processes2. The circular structure is thus set in motion and vibrates according to the physical properties of the springs and masses. The resulting dynamic motion is being scanned; that is, the positions of the masses are read and used to construct an audible waveform. The synthesis model combines aspects of Iannis Xenakis's Dynamic Stochastic Synthesis and Scanned Synthesis. It creates sounds with complex transients whose characteristics can be changed by altering the physical properties of the system, it creates a continuum between periodic and noisy sounds, and it can be used to process input sound.

In a similar way, the metal sheet acts as a vibrating object that is excited and scanned (recorded). The recorded signal is fed into the synthesis model whose output is subsequently used to excite the metal plate again. This feedback loop between synthesis model and physical model creates an entangled symmetry of excitation and scanning. The synthesis model thereby extends into a physical set-up that blurs the border between abstract model and concrete reproduction. Neither part can exist (i.e., sound) without the other, nor can the separation of empirical reality and formal model be clearly made. The model becomes something like a 'participation': an intersection of sonorous materiality and formal procedures.

Not everything, however, is determined by the set-up and the synthesis process or by a behavioural pattern dependent on input data. Instead of having organic connections between all parts of the system, there is also a scission in its structure and some decisions are not based on the input or the state of the system. These decisions control the generation of the formal temporal development of the installation. There are six independent voices, which are the result of six ways of scanning the same physical model. They form six perspectives on one object - six different paths by which to scan the object's motions. The voices initially proceed from a common starting point. They then diverge, each voice's parameters undergoing independent trajectories until only one voice remains, which forms the next starting point. There is thus an oscillation between moments of strong cohesion and moments of divergence. The durations of the trajectories are very varied; the process may thus give rise to short gestures as well as long textural transitions.

January 2012, ESC Graz.