Like bats and dolphins, some blind humans are able to echolocate — using acoustic reflections to sense, interact with, and navigate the world. However, bats and dolphins echolocate ultrasonically, at frequencies that offer higher resolution but are inaudible to humans. Inspired by advances in computing technology, we are developing a simple, low-cost device that makes ultrasonic echolocation sounds audible and allows us to explore the most useful signal properties for human observers.