iStock
A research team at the Paul Scherrer Institute (PSI) in Switzerland is developing a technique using X-ray light to digitise recordings from audio tapes that would otherwise be lost to decay.
In 1980, legendary blues artist BB King performed at the Montreux Jazz Festival. A rare recording of this performance exists on magnetic tape that has degraded to such an extent that it can no longer be directly played back using conventional methods.
In our digital world we cannot imagine that the only recording of this performance is stored on a single form of analogue media that cannot be accessed. While magnetic tapes revolutionised sound recording following their invention in the 1920s, this medium for storing audio on long, narrow strips of plastic film consisting of a magnetisable coating is not ideal for long-term archival storage as they degrade and eventually become unplayable.
In an effort to rescue this BB King audio recording, along with similar analogue magnetic media, researchers at the PSI, a research institute for natural and engineering sciences in Switzerland, have developed a method to non-destructively digitise recordings using X-ray light.
The research team, led by Sebastian Gliga, a physicist at PSI and expert in nanomagnetism, in collaboration with the Swiss National Sound Archives, have partnered with the Montreux Jazz Digital Project, which aims to restore degraded tapes and make them playable again with conventional music players.
The method the researchers are using is called synchrotron radiation. Gliga explained: “With X-ray light from a synchrotron, we can reconstruct even heavily damaged tape fragments without even touching them.”
As an example, the BB King recording can only be played back for about 10 seconds at a time due to its degraded state.
“We were not only interested in the musical content of this BB King recording, but also in taking on the challenge its state of decay presents. Synchrotron radiation may overcome the limitations of conventional restoration methods,” said Gliga.
Audio tapes store information in a layer of tiny magnetic particles that form a pattern. As the magnetic field constantly changes through the pattern, a voltage is induced in the playhead and an electrical signal is generated. This signal is amplified and converted into an acoustic signal.
In contrast, the X-ray method does not rely on the magnetic field, but on the individual compass needles that generate this field. Gliga said: “The magnetisation states of these tiny particles, whose size is smaller than a tenth of the diameter of a human hair, can be read out almost individually using the X-ray light of the SLS [Swiss Light Source] and converted into a high-quality audio signal.”
Since the synchrotron light can measure almost every single magnetic compass needle on the tape, Gliga is confident it can achieve unprecedented resolution and an almost accurate copy of the original recording.
