FIG. 4.

(Color online) α values (i.e., number of baseline SDs below baseline mean power) (a) for mean power levels across all stations; (b) at LV05, a station close (within 5.0 km) to LAS; (c) at LV10 (13.8 km from LAS); (d) at LV07, a station distal (20.8 km) from LAS. α values in the 8–500 Hz range at stations close to the airport dropped considerably after March 16, 2020. Darker blues distinguish a decline in power. The dashed, vertical lines indicate March 17, the date on which nonessential businesses were ordered to close.