The earliest audio recordings date from the middle of the 19th century. These artefacts are of significant historical interest, both from a technical standpoint – the technology was cutting edge – and the content – the novelty and complexity meant the audio recorded was often a VIP!

CLICK HERE to hear a podcast from the British Library on development of audio recovery – the original audio can be heard at 7m10s

Sadly the substrates that contain these recordings are now often too fragile to be played with original stylus methods and despite the best preservation methods, they continue to deteriorate.

Wax cylinder recording from early 20th century.
Edison tin foil recording circa 1877.

Taicaan embarked on pioneering project with the University of Southampton and the British Library to preserve these recordings for future generations: Different substrates require different surface measurement strategies. In the case of cylinder and disk recording a rotary axis is required – either normal or parallel to the axis of the imprints.

Motion system and sensor for cylinder surface mapping.
Motion system and sensor for flat recordings.
Surface map of Edision foil recording

Once individual segments of the surface have been recorded it is necessary to mathematically piece together the sections. The overall form of the measurement is largely irrelevant as it does not constitute audio information so this is also mathematically removed. The remaining data consist of the individual grooves in the surface. By tracking the minima of the grooves the path the stylus would have followed can be extrapolated.

Trajectory of stylus calculated from peak to valley separation.
Trajectory a virtual stylus takes at minima of groove converted to audio information.

Finally the vertical deviations a “virtual stylus” would have made travelling along the groove can be determined and the audio signal recovered.