In early-1930s Vienna, a physicist famous for a prediction about spinning planets helped build a machine that recorded sound on paper. The Selenophone printed four soundtracks side by side on a paper strip, and a single 300-meter roll held about 70 minutes of audio, roughly what ten double-sided gramophone records could carry.
The system came from the Selenophon Licht- und Tonbildgesellschaft, a Vienna company founded in 1929. Its inventors were the physicist Hans Thirring and Oskar Czeija, then director general of RAVAG, Austria’s radio company. Czeija also handled the special copying paper the process needed, filing several patents of his own and setting up a firm to make it.
How do you play a sheet of paper?
Early talking pictures already stored sound as light. A sound wave was turned into a strip of varying light and dark on film, and in the cinema a lamp shone through that strip onto a photoelectric cell, which turned the flicker back into an electrical signal and then into sound.
Paper is not transparent, so the Selenophone could not shine light through it. A 1933 handbook for amateur filmmakers explains the fix: the light was reflected off the paper instead, and the cell read the bounce. The same book describes a second twist. The sound was captured photographically first, but copies were mass-produced like a newspaper. The photographic track became a metal plate, then a rubber “blanket” used as a printing roll, so tracks could be inked onto cheap paper by the meter.
The heart of the player was a selenium cell, which is where the name comes from. Thirring’s cell was more sensitive to low tones than the alkali photocells rivals used, though it was weaker in the treble. Because the Selenophone needed less amplification, it was less prone to the distortion that heavy amplification could cause.
What 70 minutes on a roll meant
The 1933 handbook pitched the Selenophone not as a cinema projector but as a gramophone replacement. The numbers show why that was tempting. If ten double-sided records equal 70 minutes, each record held about 7 minutes, or roughly 3.5 minutes a side (70 divided by 10 is 7, and 7 divided by 2 is 3.5). One paper drum swapped out a stack of brittle discs and nine record changes.
The company’s later “U 7” machines were good enough that, according to the German-language encyclopedia entry on the firm, conductor Arturo Toscanini chose Selenophon tapes rather than discs to record performances at the Salzburg Festival, and major American radio networks also used them. The same entry calls the Selenophon method a forerunner of magnetic tape recording.
A short life
The company produced Austria’s first homegrown sound films from the summer of 1929, ran an international newsreel from 1931 to 1933 and made feature films until 1932, when it struck a deal with the German sound-film giant Tobis-Klangfilm that split the Austrian market. In 1937 it introduced the first film dubbing facility in Austria.
It did not survive 1938. After Austria’s annexation that March, the company was dissolved, and Czeija was forced to sign over its patents for one Reichsmark each. Thirring, who in 1918 had predicted the Lense-Thirring frame-dragging effect in general relativity with mathematician Josef Lense, was forced out of his University of Vienna post the same year and reinstated after the war.
For more forgotten tech history, see our story on the 1974 Utah teapot that became computer graphics’ favorite test model, or our account of Wilhelm Röntgen spotting X-rays in 1895. The Selenophone’s own roll length is the detail that lingers: 300 meters of printed paper for 70 minutes of sound.
Further reading
Image: Beate Pamperl, CC BY-SA 4.0 via Wikimedia Commons
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