The Singing Arc

1. The Singing Arc 1988 William Du Bios Duddell

2. Creation • Before the invention of the Electronic light bulb in America, Carbon Arc lamps were widely used throughout Europe. The lamps generate light by a spark between two carbon nodes. This process also produced a humming sound. The British physicist William Duddell was elected to solve the problem. During his experimentation, Duddell found that he could manipulate the audible frequencies when varying the voltages supplied by the lamps. Duddell then attached a keyboard to the lamps creating The Singing Arc, one of the first electronic instruments audible with out an amplification device.

3. Despite the potential of the instrument, the Singing Arc became nothing but a novelty. Later it was found that one could attach the Singing Arc to an antenna and be made to 'sing' at radio frequencies, so instead of using for audio, it was used for a continuous radio transmitter.The use of Carbon Arc lamps were also utilized by Thaddeaus Cahill when creating the Telharmonium 10 years later.

4. How It works • William Duddell found that with the slightest alteration in the current passing through the arc caused a change in the hot vapor column surrounding the ends of the carbons which produced audible sounds. He found that by using the shunt circut he could control the vatriation to obtain a musical scale. Duddell then formed an arc with solid carbons then using a shunt circut containing capacity and self inductace and ingenious keyboard, he created one of the first electronic instruments.

5. How it Works • “a current arc between two electrodes, shunted by a circuit containing a capacitance and inductance would establish an oscillating circuit. The value of the of the capacitance and inductance determines the frequency of oscillation. An arc follows a characteristic, which is the inverse of Ohm's law in that when the current of the arc is increased, the voltage across the electrodes decreases. This characteristic is often called negative resistance. Placing a series LC circuit across the terminals of an arc will initially cause the capacitor to charge, diverting some of the current away from the arc. Given the aforementioned arc characteristics, the potential difference between the arc electrodes will increase, putting the capacitor at an even higher voltage. Once the capacitor reaches full charge the arc current will reverse to discharge the capacitor back into the arc. As the current into the arc increases, the potential difference will fall and the voltage across the capacitor will also fall to a point, which it will begin to charge again. If the circuit resistance is small enough, this process will continue as an oscillation. Duddel found that it was necessary to use a minimum of 1 microfarad of capacitance to obtain oscillations of considerable energy. With this large capacitance, it was not possible to reach high enough frequencies for transmission of Radio-telegraphy.). “ • http://120years.net/machines/arc/index.html

6. Some Evolution • The Plasma speaker which functions by the sound moving thorough a corona discharge or electronic arc, showing the evolution from the Singing arc.