Stuart Hyatt returns with another sonic wonder in the Field Works series, bringing the listener into truly uncharted acoustic territory. Ultrasonic is perhaps the first-ever album to use the echolocations of bats as compositional source material. For this special album, Hyatt has assembled an extraordinary group of contributors: Eluvium, Christina Vantzou, Sarah Davachi, Ben Lukas Boysen, Machinefabriek, Mary Lattimore, Felicia Atkinson, Noveller, Chihei Hatakeyama, John Also Bennett, Kelly Moran, Taylor Deupree, Jefre Cantu-Ledesma, Julien Marchal, and Player Piano. Ultrasonic is part of a broader storytelling project about the federally endangered Indiana bat. Generously funded by the IUPUI Arts & Humanities Institute and the National Geographic Society, each album contains an official printed booklet of The Endangered Species Act of 1973.