Preliminary sonification of ENSO using traditional Javanese gamelan scales
Abstract
Parameter-mapping sonification of ENSO data preserves dynamical signatures through acoustic phase space analysis, revealing distinct coupling regimes in traditional musical scales.
Sonification -- the mapping of data to non-speech audio -- offers an underexplored channel for representing complex dynamical systems. We treat El Niño-Southern Oscillation (ENSO), a canonical example of low-dimensional climate chaos, as a test case for culturally-situated sonification evaluated through complex systems diagnostics. Using parameter-mapping sonification of the Niño 3.4 sea surface temperature anomaly index (1870--2024), we encode ENSO variability into two traditional Javanese gamelan pentatonic systems (pelog and slendro) across four composition strategies, then analyze the resulting audio as trajectories in a two-dimensional acoustic phase space. Recurrence-based diagnostics, convex hull geometry, and coupling analysis reveal that the sonification pipeline preserves key dynamical signatures: alternating modes produce the highest trajectory recurrence rates, echoing ENSO's quasi-periodicity; layered polyphonic modes explore the broadest phase space regions; and the two scale families induce qualitatively distinct coupling regimes between spectral brightness and energy -- predominantly anti-phase in pelog but near-independent in slendro. Phase space trajectory analysis provides a rigorous geometric framework for comparing sonification designs within a complex systems context. Perceptual validation remains necessary; we contribute the dynamical systems methodology for evaluating such mappings.
Community
This study presents a novel approach to climate data sonification by mapping the El Niño-Southern Oscillation (ENSO) Niño 3.4 index (1870–2024) onto traditional Javanese Gamelan scales, treating the auditory display itself as a complex dynamical system. By encoding the data into Pelog (unequal intervals) and Slendro (near-uniform intervals) tuning systems, the authors reveal that the musical framework fundamentally alters the geometric topology of the output: Pelog scales induce a strong anti-phase coupling between spectral brightness and energy, whereas Slendro scales allow these dimensions to vary independently. Using phase space trajectory analysis and recurrence quantification, this article demonstrates that these mappings preserve key dynamical signatures of the source data, such as its quasi-periodicity, with "alternating" composition modes exhibiting high recurrence rates analogous to periodic orbits. This work argues that cyclical, culturally grounded musical structures like Gamelan offer a rigorous, structure-preserving alternative to Western equal temperament for representing the non-linear dynamics of climate chaos.
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