Each district shaded by two things at once: household income (left→right) and the share of residents above a chosen noise level (bottom→top). Move the threshold and watch which way the two align.
Reading it. A magenta district is both loud and affluent; a deep-blue one would be loud and poor. Barcelona's loud districts are mostly magenta — the central, dense, amenity-rich ones (l'Eixample above all) — while its quietest are a mix of the humblest (Nou Barris) and the leafy uptown. Raising the threshold only strengthens the alignment: the very loudest exposure is concentrated in the wealthier districts, the reverse of how air pollution falls. Income index: household disposable income per capita, Barcelona = 1.00 (2019). Noise: Mapa Estratègic de Soroll, Lden, all sources (2022).