The Syracuse University Library Radius Project: Development of a non-destructive playback system for cylinder recordings

Syracuse University Library's Belfer Audio Laboratory and Archive (Belfer) holds nearly 20,000 cylinder recordings produced during the 'cylinder era' of 1895-1929. Many cylinders have become deteriorated over the past one hundred years and cannot be played without suffering serious physical damage inflicted by the sharp styli (needles) of traditional mechanical playback machines. In some cases, even one pass of a stylus may irrevocably damage a cylinder. In response to the playback challenges of cylinder recordings, Syracuse University Library developed the Radius Project: Development of a Non-Destructive Playback System for Cylinder Recordings, funded by the Institute of Museum and Library Services. Recorded sound on a cylinder is represented by the alternating motion/velocity of the groove over a period of time. In order to capture sounds from cylinders in a non-destructive way, the Radius Project developed a prototype playback system that uses a laser beam to interrogate the cylinder. The system reconstructs sounds from cylinders by using an optical heterodyne interferometer to exploit the temporal, rather than spatial, coherence of the laser. The interferometer obtains a precise measurement of the Doppler frequency shift (the rate of change of optical phase shift) caused by the motion of the modulated groove in the cylinder, using wavelength of light as the unit of measure. The ability of the Radius system to measure the rate of change of optical phase shift may provide the optimal approach for reconstructing historically accurate sound from cylinder recordings. Successful completion of the Radius system will provide Belfer with the capability to preserve the sonic content of previously inaccessible cylinder recordings by producing high fidelity, historically accurate analog reproductions. In turn, and as copyright permits, Belfer will also be able to meet the changing needs and expectations of twenty-first century learners by contributing high fidelity, historically accurate digitized sounds from cylinders, thereby enriching the historical content of the World Wide Web