A network of historians, audio engineers and scientists are working to preserve the earliest audio recordings ever made.

The earliest known recorded human sounds have been discovered, a recording made some 20 years before Thomas Edison invented the phonograph.

(CNN) — Thomas Edison came up with a way to play back recorded sound in 1878. But 20 years before the inventor patented the phonograph, French scientist Édouard-Léon Scott de Martinville was fiddling around in his laboratory trying to come up with a way to record sound. His invention, the phonautogram, enabled him to create a visual representation of his voice.

Scott de Martinville wasn’t able to listen back to his recordings, though. The science of acoustics was in its infancy. He could only see lines etched in soot. His achievements were long-forgotten until a group of historians, audio engineers and scientists searched for his work. The First Sounds Collaborative found it in the archives of the French Academy of Sciences in 2008.

“His machine would capture the vibrations out of the air and write them on to a moving piece of paper,” said David Giovannoni, one of the founders of First Sounds. “When you look at the writing that this machine made, it looks exactly like a sound wave would look on audio editing software today.”

Giovannoni and his group analyzed Scott de Martinville’s work with audio software and unlocked the sound held in the waveforms. The result is like listening to a ghostly time machine, the voice of a man from 150 years ago singing French song “Au Clair de la lune.” The earliest known sound recordings can be heard at www.firstsounds.org.