Sound Ledger: Bird Song, Misophonia

100,000: Number of songs in a study of bird song evolution.

21,000: Number of hours of audio in the bird song study. 

18: Percent of the (human) population that may suffer from misophonia (a significant adverse reaction to certain sounds), 

Sources: bird song (npr.org), misophonia (nautil.us — thanks, Rich Pettus!).