Virtual Acoustics, Feedback, Disklavier, University of Limerick, Stanford University, CCRMA, Alvin Lucier, Cathy van Eyck, Steve Reich, Hagia Sophia, Altemps, Max MSP, Samuel Beckett
Live experimental sound practices have explored the use of audio feedback for over sixty years. Such feedback is primarily dependent on the geometries of the space and the position of the sound system in that space. Thus the question arises, within the fixed geometry of a performance space, how might one go about modifying the acoustic characteristic of this space so that different qualities of feedback can be achieved with minimal interventions? Recent advances have seen virtual acoustic systems that enable us to simulate the acoustic characteristics of one space inside another, opening up many aesthetic and artistic possibilities. In this paper we describe a novel method for adapting a virtual acoustic system to create audio feedback effects for live experimental sound and music performances. The virtual acoustic system employed in our work is built from standard room microphones and loudspeakers, running auralizations generated with low latency convolution reverb. Any potential loop gain feedback that would normally occur due to the close proximity of the systems’ microphones and loudspeakers is suppressed based on system measurements. By inserting a variable length delay into the system’s feedback suppression signal paths – what we call the cancellation signal paths – we temporarily generate a variety of audio feedback frequencies. Further, and most importantly, since the virtual acoustic system is fundamentally a reverberation system, the sound of this feedback is heavily influenced by the acoustics of the virtual space. Several demonstrations of these phenomena are presented in isolation and in the context of a recently composed multimedia work.