From Keystrokes to Auditory Textures: Structural Acoustic Analysis of an Emergent Haptic Soundscape.

This paper examines emergent environmental haptics via structural acoustic analysis of Babbling Brook, a large-scale installation of forty solenoid-actuated computer keyboards (eighty solenoids) and an eight-channel synthetic keystroke layer. Whereas most arts-haptics research addresses direct-contact interfaces and wearables for individual users, environmental phenomena are difficult to measure in walk-through galleries and have received little attention. The work spans four density modes: at low densities listeners perceive discrete keystrokes, while at high densities the auditory texture approaches a continuous, broadband, noise-like regime reminiscent of running water. Because direct measurement was not possible in the gallery, we analyze the installation's audio as an acoustic proxy for the underlying haptic transformation, using seven DSP metrics of signal stationarity and auditory-texture perception (e.g., crest factor, waveform kurtosis, spectral flux/spread). Three mechanical keyboard models with distinct switch mechanisms are compared, and natural water recordings serve as an external reference. Across modes, four of seven metrics differ with large effect sizes (Kruskal-Wallis $H > 8.6$, $p < 0.035$, $\eta ^{2} > 0.70$): keyboard-specific profiles distinct at sparse densities converge at high densities as waveform statistics approach Gaussian values. Mode IV swarm statistics overlap the water reference on five of seven metrics and are smoother on the other two, indicating that the swarm enters water's broadband stationary regime but lacks its macroscopic fluctuations. These results provide quantitative acoustic evidence supportive of an emergent perceptual transformation toward environmental haptics in the arts; direct vibrotactile and perceptual validation are identified as future work.