Set a traffic drone at the window, add a natural masker beside it, and read the estimated soundscape pleasantness — the perceptual outcome, not the level.
Inputs · received at the façade (immission)
The steady road or plant hum as heard indoors — an immission level, not the source's emission.
Birdsong lifts pleasantness most; a fountain helps mainly against a steady drone.
At 30 dB the masker is effectively off. Raise it and watch where extra sound stops helping.
Method · Pleasantness is estimated from the balance of perceived sound sources after the predictive model of Mitchell et al. (2021) and scaled to the ISO 12913-3 range [−1, +1]. Natural-sound dominance rises as the masker approaches the drone; a loudness term after De Coensel et al. (2011) penalises the higher overall level a masker adds, so past an optimum extra masker only costs pleasantness, and the drone still sets the ceiling. Coefficients are indicative, not a reproduction of the source regressions.