Relationship between average outdoor and indoor levels (left) across all receivers and sound sources in Format L1 for Room 1 with the façade structure composed of a double-leaf window and wall surface, including the time-averaged equivalent spectral outdoor-to-indoor level differences (right). Note that “°"/“×" (levels per 15 s) and “—"/“ - -" correspond to h _w = 0.1m/0.2m, while d _g denotes the window cavity width. Values in the legend denote window thicknesses.