Despite the invention of the incandescent electric light bulb ( Thomas Alva Edison and Joseph Swann, 1880) Carbon Arc Lamp were commonly used for street lighting and industrial applications – and remained so until the beginning of the twentieth century when developments in the lightbulb made the arc-lamp obsolete.
The Carbon Arc Lamp generated light by creating a bright spark between two carbon nodes. The problem with this method of lighting, apart from the dullness of the light and inefficient use of electricity was a constant humming, shrieking or hissing noise emitted by the electric arc.
The British physicist and electrical engineer William Duddell was appointed to solve the problem in London in 1899. During his experiments Duddell found that by varying the voltage supplied to the lamps he could create controllable audible frequencies from a resonant circuit caused by the rate of pulsation of exposed electrical arcs.
Duddell’s investigations revealed that the cause of the arc-lamp noise was the nonlinear nature of the arc that resulted in a negative resistance. This phenomena had already previously been recorded in 1898 by a Dr. Simon (Frankfurt, Germany). Dr. Simon had noticed that the electric arc could be made to “sing” by means of modulating the voltage to an electric arc supply. Dr. Simon showed that the electric arc made a effective loudspeaker which he demonstrated in public. (Dr. Simon’s experiments also showed that the modulated arc produced not only sound but a modulated light beam by means of which the German Navy managed to make telephone calls between ships using a modulated arc searchlight and a photosensitive selenium cell.)
Duddell,who may have been aware of Simon’s work, tried to solve the noise by adding a LC resonant circuit across the arc and in doing so he created a tuneable oscillator. By attaching a keyboard that varied the voltage input to the circuit Duddell created one of the first electronic musical instruments. Duddell’s invention the only ever electronic instrument to use an electrical arc to generate sound and the first electronic instrument that was audible without using the yet to be invented amplifier, loudspeaker or telephone system as an amplifier and speaker.
When Duddell exhibited his invention to the London institution of Electrical Engineers it was noticed that arc lamps on the same circuit in other buildings also played music from Duddell’s machine this led to speculation that music delivered over the lighting network could be created.
“All three arcs were found to be supplied with current from the street mains, and it was clear that this main current had been varied in such a way by Mr. Duddell’s keyboard as to reproduce in the two other laboratories the tunes which he supposed he was playing only to his audience in the lecture room…This obviously meant that by playing on one properly arranged keyboard tunes could be reproduced in a number of different arcs and at a distance from the musician.“
MUSIC IN ELECTRIC ARCS.; An English Physicist, with Shunt Circuit and Keyboard, Made Them Play Tunes. New York Times, April 28, 1901,Page 7
Duddell didn’t capitalise on his discovery and didn’t even file a patent for his instrument. Duddell toured Britain with his invention in 1898 which unfortunately never became more than an amusing novelty; Duddell left the frequency within the audible range but later in 1902 Danish electrical engineers Valdemar Poulsen and Peder Pedersen realised that Duddell’s singing arc would function as a radio transmitter if the circuit was tuned to radio, rather than audio, frequencies.
The carbon arc lamp’s audio capabilities was also used by Thadeus Cahill during his public demonstrations of his Telharmonium ten years later.
Biographical Information: William du Bois Duddell.
UK 1 July 1872 – 4 November 1917
William Duddell an electrical engineer in Victorian England was famous for developing a number of electronic instruments notably the “moving coil oscillograph” an early oscillator type device for the photographic monitoring of audio frequency waveforms. Other inventions of Duddell’s included the thermo-ammeter, thermo-galvanometer (an instrument for measuring minute currents and potential differences later used for measuring antenna currents and still used in modified form today)and a magnetic standard, which was used for the calibration of ballistic galvanometers.
‘Some Experiments on the Direct-Current Arc’, Nature, vol. 63, no. 1625 (December 20, 1900), pp. 182-183.
Wireless: A treatise on the theory and practice of high frequency electric signalling. L.B.Turner. Cambridge University Press. 1931
‘The electrical imagination sound analogies, equivalent circuits, and the rise of electroacoustics, 1863-1939′ Roland Wittje Osiris, ISSN 0369-7827, 28, 2013, p. 40-63