Music and Audio Computing Lab

Main menu: Home | People | Research | Publications | News |

Audio Feedback Systems for Evolutionary Sound Generation

Audio feedback is an acoustic phenomenon that occurs when sound played by a loudspeaker is received by a microphone to create a persistent loop through a sound system. While audio feedback is generally regarded as an undesired situation, for example, when a public address system manifests an unpleasant howling tone, there have been numerous artistic examples and compositions that make use of its tone-generating nature. Jimi Hendrix is an oft-cited example of how electric guitar players create feedback-based tones by holding their instruments close to the amplifiers, and Steve Reich’s Pendulum Music (1968) features phasing feedback tones generated by suspending microphones above loudspeakers.

Aiming for high-level intentional control of audio feedback, we present a system adapting toward chosen sonic features. Users control the system by selecting and changing feature objectives in real-time. The system has a second-order structure in which the internal signal processing algorithms are developed according to an evolutionary process. Genotypes develop into signal-processing algorithms, and fitness is measured by analysis of the incoming audio feedback. A prototype is evaluated experimentally to measure changes of audio feedback depending on the chosen target conditions. By enhancing interactivity of an audio feedback through the intentional control, we expect that feedback systems could be utilized more effectively in the fields of musical interaction, finding balance between nonlinearity and interactivity.

We also suggest another audio feedback system which generates desired sonic behaviors by enriching the influence of existing acoustic information such as room response and ambient noise. This ecological approach to audio feedback emphasizes mutual sonic interaction between signal processing and the acoustic environment. Mappings from analyses of the received signal to signal-processing parameters are designed to emphasize this specificity as an aesthetic goal. Our feedback system presents four types of mappings: approximate analyses of room reverberation to tempo-scale characteristics, ambient noise to amplitude and two different approximations of resonances to timbre. These mappings are validated computationally and evaluated experimentally in different acoustic conditions.



  • Augmenting Environmental Interaction in Audio Feedback Systems
    Seunghun Kim, Graham Wakefield and Juhan Nam
    Applied Sciences, 2016 [pdf]
  • Sonic Participation in the Evolving Audio Feedback System
    Seunghun Kim, Changheun Oh, Graham Wakefield and Juhan Nam
    The 22nd International Symposium on Electronic Art (ISEA), 2016 [pdf] [website]
  • Augmenting Room Acoustics and System Interaction for Intentional Control of Audio Feedback
    Seunghun Kim, Graham Wakefield and Juhan Nam
    Proceedings of the 41st International Computer Music Conference (ICMC), 2015 [pdf]
  • Toward Certain Sonic Properties of an Audio Feedback System by Evolutionary Control of Second-Order Structures
    Seunghun Kim, Juhan Nam and Graham Wakefield
    Proceedings of the 4th International Conference (and 12th European event) on Evolutionary and Biologically Inspired Music, Sound, Art and Design (EvoMUSART), 2015 [pdf]


Seunghun Kim, Graham Wakefield (York University) and Juhan Nam