Akoetrope  Aernoudt Jacobs May 2019 -

A first proof of concept is being built that is both an intuitive and heuristic device for understanding the persistence of sound cognition. The device is freely inspired from the Phénakisticope/Zootrope devices that were invented around 1833. It uses the phenomenon of iconic memory or persistence of vision to create a moving image. In the auditory domain we can find a similar phenomenon called echoic memory. Both phenomena rely on short term sensory memory information that lingers on the threshold between perceiving and remembering.

Comparing the visual to the auditory phenomenon, the persistence of an image is at 1/5 of a second (5 images per second) and persistence of a sound is clocked at 1/20 of a second (20 oscillations per second or 20Hz). The cognition in the auditory domain is very complex, it evolves and shifts through very distinctive perceptual thresholds along the frequency bandwidth, and equally, the processing of those sounds takes place in very different parts of the brain. 20 Hz (or 20 oscillations per second) is an important threshold that differentiates rhythm from tones. Until that threshold rhythms and beats are still perceived as non-continuous. Until this threshold sound patterns are perceived as periodic rhythms and processed in the left hemisphere of the brain. At rates above 20 Hz individual beats and impulses can’t be segregated. They are too fast to be differentiated and will blend into a continuous tone. Another important fact is that from this point sounds are processed in the right hemisphere of the brain. At 40Hz, pitch differences will emerge in our perception, and at this point pitch and melodies will appear. Between 40-80Hz human can clearly detect pitch intervals and recognize relations between chords and melodies.

The research is carried out with a rotating acoustic device that carries a multichannel speaker system, oscillators and a granular sequencer. It will be a device that enables auditory deceptions, combining speculative frequencies and ambiguous speech articulations. It is a device that challenges the way we perceive sounds, challenging our hearing by playing with the psycho acoustics and the physical limitations of the hearing organ. The device enables the recognition of patterns by re-fragmenting a sequence so that it becomes recognizable. It will be developed further as a performative drone instrument enabling for example aliasing distortions and shifting sonic moiré patterns.