Fig. 4.

Median noise exceedance, i.e., the amount that anthropogenic noise increases sound levels above the natural level, in protected areas across the continental USA. Noise exceedance of 1.25, 3.01, 6.02, and 10 dB corresponds, respectively, to 25, 50, 75, and 90% reductions in listening area, i.e., the area at which an acoustic signal can be detected by humans. Gray areas are outside the protected area network. Reprint from Buxton et al. (2017) with permission from the American Association for the Advancement of Science (AAAS) under a Creative Commons Attribution Noncommercial License 4.0 (CC BY-NC)