The Universe of Discourse

Thu, 16 Feb 2006

More low-tech sound recording
In an earlier post, I wondered how Robert Hooke could have discovered the frequency of a vibrating string in 1664. I suggested a device involving a bristle that traced a sinusoid on a smoked glass plate. I was sure that I head heard about this somewhere before, and wasn't making it up.

With the Wonders of the Internet, such things are easy to look up. Google for "bristle" and "smoked glass" and there you have it. The device is called a "phonautograph", and was invented in 1857 by Leon Scott. So the idea does work, but was probably not what Hooke used. My search continues.

The phonautograph was one of Alexander Graham Bell's inspirations for the telephone. Bell, whose principal research area was to improve education of deaf persons, built a phonautograph of his own, using—get this—an actual human ear. The bristle was attached to the ossicles. He cut away the stapes bone, and attached a wheat straw to the incus. I wonder whose ear he used?

I've read that a phonautograph recording survives from around 1860 and is the oldest known sound recording, although there was no way to play it back until recently, when the tracing was digitized and given to a computer to synthesize.

There was some talk a few years ago about the possibility that clay pots might retain recordings of the ambient sounds from the time they were created: they are thrown on potters' wheels that revolve at a uniform speed; they have high recording resolution, and are frequently worked with sharp tools that would have left grooves in them much like the grooves of phonograph records. I saw an exhibit of this in a science museum somewhere, but I could not make anything of the sound that they recovered from the pot, even though it had been specially constructed for the purpose. There are obvious, major problems with the idea, but it's nice to think that we might someday be able to listen to sound recordings of Sumerians chatting in the potter's workshop.

Come to think of it, conventional phonography was pretty low-tech itself, until the introduction of magnetic and later digital media.

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