A device in the basement of the Library of Congress produces images of sound, echoing the reason recording devices were invented in the first place

When recorded sound was in its infancy, more than 150 years ago, inventors still hadn’t answered what was, to them, a fundamental question:

What does sound look like?

They knew what sound sounded like, of course, and even what it felt like but what would it mean to see sound on paper? It was this question that inspired the French inventor Édouard-Léon Scott de Martinville to design the phonoautograph, which is widely considered the earliest sound-recording machine. His theory was that if he could build a device that transcribed sound, he could read sound the way we read text. +