During World War II, many radio stations recorded their programming on lacquer transcription discs manufactured with a glass base instead of the typical aluminum base, since aluminum was in demand for the war effort. Over the years, many of these glass discs have broken and cracked.
The New York City Municipal Archives has carefully preserved several rare glass discs that had been broken in the past, in hopes that a technology would come along one day that would be able to retrieve the sound. That day is here!
Indeed, this spring Marcos Sueiro Bal and John Passmore of the New York Public Radio Archives brought several of these fragile discs to NEDCC as part of the pilot project for the Center’s IRENE system. Many of these discs have unique content originally broadcast on radio station WNYC, which at the time was part of the City of New York as the “Municipal Broadcasting System."
Berkeley Labs had accomplished successful testing on broken media during their development of
One of the discs was a radio broadcast from Christmas Eve 1943, dedicated to the U.S. soldiers at war around the world —an NBC production that was likely broadcast on WNYC as well. The disc was broken into five pieces and NEDCC Audio Preservation staff was able to fit the pieces closely together on the turntable under IRENE’s lens and image the grooves.
Though IRENE’s platter turns at a much slower rate than the intended playback speed of the discs (~1 ¼ RPM), keeping the pieces stable and in-focus throughout the scan was a challenge. After a few tries, we were able to align the disc and produced images like the one below.
Even with careful alignment, the grooves were not perfectly continuous in the image, so the tracking was drawn manually in software, then partially automated in a process that took several hours, but produced a transfer that wouldn’t have been possible before IRENE.
You may notice from our audio sample that the sound is still quite noisy. Lacquer discs frequently exude fatty acids as a result of the breakdown of a plasticizer additive. This exudate covers the grooves and adds noise to mechanical and optical transfers alike. We are currently researching ways to clean this from the disc without risking damage to the delicate lacquer surface.
(Click the sound bar for audio.)
One of the greatest benefits of the IRENE system will be its ability to safely recover sound from unique or rare recordings, broken or damaged media, and media that are too delicate to play with a stylus. We look forward to the unfolding stories of discovery as we make the IRENE technology available to cultural institutions across the nation!