Amazingly, today a "new" oldest recording has been found and played back. It was once thought that Thomas Edison singing a childrens' song back in 1877 was the oldest sound recording, but not anymore. The "new" oldest is a recording made in 1860 by a French scientist called Au Clair de la Lune.
Originally, Au Clair de la Lune only wanted to see sound visually and never intended it to be a recording, but a group of audio historians have used a Virtual Stylus to decrypt the paper and have produced an eery sound. The sound was captured using a Phonautograph; a device that etches sound waves onto paper covered in soot from a burning oil lamp. The lines were created by a needle which vibrated when nearby sounds touched the attached diaphragm (image to the right.)
The BBC article can be found here, from there you can listen to the recording if you click the Ancient audio link under the image. I must say it is very scary to think of a this man recording this sound almost 200 years ago and here's me sitting on my personal computer. Rather unsettling.
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