Groovy Pictures: Extracting Sound from Images of Old Audio Recordings

Article excerpt

Songs and words preserved on antique vinyl records and wax cylinders become more precious with each passing day. They also grow increasingly fragile and are especially vulnerable to damage if played.

Now, researchers using optical-scanning equipment have made exquisitely detailed maps of the grooves of such recordings. By simulating how a stylus moves along those contours, the team has reproduced the encoded sounds with high fidelity.

Libraries with collections of old recordings "don't want to queue up an antique piece of material every time you want to hear it," notes particle physicist Carl H. Haber of Lawrence Berkeley (Calif.) Laboratory, codeveloper of the new scanning approach. Instead, those institutions seek to extract sound from delicate recordings and preserve it electronically. In that form, it can be played back repeatedly without harming the original and also made available on the Internet.

A few years ago, Haber heard on the radio that archivists needed ways to non-destructively extract sound from old recordings. He and his Berkeley lab colleague Vitaliy A. Fadeyev, who make arrays of sensors for tracking minute particles in powerful accelerators, realized that their own work was relevant. To align their arrays, they scan sensor surfaces by using a microscope with submicrometer resolution. After hearing of the archivists' problem, "we thought, 'Wow! Why don't they just do it optically?'" Haber recalls.

The scientists used their microscope to make a two-dimensional map of the grooves on a 78-revolutions-per-minute shellac disc of a circa 1950 recording of "Goodnight Irene. …