Controlled miniature acoustic feedback environments, electronic feedback loops, RF leakage and radiated emissions, crosstalk, hum, microphonics; emissions from computer installations, ECG and diathermy machines, photocopiers. Audio feedback (the squealing heard when a microphone picks up its own amplified signal) is a paradox of self-reference, a short-circuit audio path that loops to infinity. Feedback is analogous to micro-miniature self-organising systems and phenomena, cellular automata, chaotic systems and chemical self-organisation.