Disrupting unruly fans

Sander J. van Wijngaarden and Johan A. van Balken (2007), "Theoretical feasibility of suppressing offensive sports chants by means of delayed feedback of sound," Journal of the Acoustic Society of America, 122/1, 436-445.

A novel approach for disrupting offensive chants at sporting events is proposed, based on attacking synchronization between individuals. Since timing is crucial for coordination between chanters, disruption of timing is expected to be effective against undesired chants. Delayed auditory feedback is known to disrupt timing in individual sound production. It may be expected to have similar effects on groups of chanters. To test this hypothesis, a controlled laboratory study was carried out. This showed that the timing of individuals joining in with sports chants can indeed be severely disrupted by also presenting an artificially delayed version of this chant (distracter). This effect is reduced as an individual is given more cues (direction, fidelity) to differentiate between original chant and distracter. However, informal field trials showed that it may be hard to exploit the perceptual effects discussed here for countering offending sports chants in a real-life setting, particularly due to feedback distortion at the required high levels. ©2007 Acoustical Society of America

Perhaps this technique could also be used to prevent clapping between movements.