The Singing Bridge: Sonification of a Stress-Ribbon Footbridge

Abstract

Stress-ribbon footbridges are often prone to excessive vibrations induced by environmental phenomena (e.g., wind and rain) and human actions (e.g., walking and jumping) and their liveliness is strongly associated with their slenderness.In earlier studies, multiple dynamic responses of a stress-ribbon footbridge were observed on the campus of the Faculty of Engineering of the University of Porto (FEUP) in Portugal. Although extreme vibrations have never been reported, vertical oscillations are clearly perceptible under pedestrian excitement. While monitoring the bridge, the technology revealed physical phenomena that are invisible to humans. This project aims to adopt sonification techniques as a compositional tool to create a sonic manifestation that shows the dynamic response of the bridge.In this study, two different sonification techniques (audification and parameter mapping) were used to extrapolate the same phenomena using different strategies. For what concerns sound synthesis, the first technique used an FM synthesizer, while the second one used external VSTs and generative approaches to create a compelling musical sonification.In order to evaluate the proposed sonification techniques' reliability, an online listening test was conducted to assess the three main dimensions of a collected dataset: the number of people crossing the bridge, their walking speed, and the steadiness of their pace. Respondents were required to complete both a blind test and one after a short training to assess the intuitiveness and reliability of both methods.According to the results, it is clear that the training significantly improves the participants' accuracy in identifying the correct categories. In fact, almost all values have increased after the short training. Therefore, this suggests that the success of both sonification techniques could improve significantly with deeper training. Additionally, the overall trend shows parameter mapping sonification as a more intuitive and precise technique than audification.