Nussbaumer System

Helmut Jäger
The First Wireless Transmission of Music

Otto Nussbaumer was born on 31 March 1873 in Wilten, Innsbruck, and from 1901 to 1907, immediately after graduating, was an assistant in the post of “constructor” to Professor Dr. Albert von Ettingshausen at the Chair for Physics and Electrical Engineering at the Graz Technical University. His duties involved not only the teaching of the practical course but also the preparation of a variety of demonstration experiments for Ettingshausen’s lectures. These experiments included some in the extremely new field of radio telegraphy.

Taking as his starting point experiments with what was known as the singing arc, in which Nussbaumer fed the electrical oscillations to the input circuit of a Braun radio transmitter, he succeeded in making the sound of the arc audible in a simple Marconi receiver consisting of an aerial, headphones and a detector. The latter had been developed by Nussbaumer especially for this purpose. It consisted of partially oxidized iron filings embedded between two electrodes, an arrangement later discovered to have the same effect as a rectifier. This success encouraged Nussbaumer to use this method to transmit sounds generated by musical instruments. For this purpose, he used two different alternative circuits. In the simpler version, he replaced the inductor interrupter in the transmitter input circuit by a carbon microphone that could take a current of a few amperes. After protracted preliminary trials, his attempts met with success on 15 June 1904. Sounds of musical instruments placed before the microphone were clearly audible in the headphones of the receiver system, the different instruments being easily recognizable. Attempts to transmit speech in the same way failed. As we now know, the vibration spectrum is too complicated.

Nussbaumer’s experiment was surprising, the prevailing opinion among scientists being that such transmissions using a radio transmitter were impossible as a matter of principle because it could only transmit short high-frequency wave trains that were relatively far apart. Nussbaumer was most probably the first to achieve a wireless transmission of acoustically generated sounds using high-frequency electromagnetic waves. He was certainly the first to publish his invention in a recognized academic journal¹, and, a very important aspect, the experiment was successfully repeated on several occasions by others using the same apparatus many years later. Nor was his pioneering role in this field ever contested in writing. However, his invention was of no relevance in the development of the radio. It was only two years later that the Dane Poulsen using a light arc resonant circuit, and the American Fessenden using a dynamo machine, succeeded in producing sufficient high-frequency continuous waves and overlaying them with acoustic frequencies, thus enabling the transmission of both music and speech. Until recently, it was not clear what kind of waves had been transmitted by Nussbaumer’s device, and it was only a repeat of Nussbaumer’s experiment at Graz Technical University in 2004 as part of a memorial ceremony that answered the question.

Otto Nussbaumer resigned from the University in 1907 and, after one year with the State Construction Service in Graz, moved to the Salzburg Provincial Building Department, working his way up to head of the section for mechanical engineering and electrical engineering. He died on 15 January 1930.

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