Valdemar Poulsen, Danish telephone engineer and inventor, patented the Telegraphone in 1898. It was the first practical apparatus for magnetic sound recording and reproduction. It recorded, on a wire, the varying magnetic fields produced by sound. The magnetized wire could then be used to play back the sound.
Valdemar Poulsen (1869 - 1942)
Valdemar Poulsen, son of a Danish High Court judge was born 23rd November 1869. At the age of 24, he obtained a position in the technical section of the Copenhagen Telephone Company. There seems to be no record of what gave Poulsen the idea of magnetising steel wire to make sound recordings. Maybe he had read an article written in 1888 by American scientist Oberlin Smith for the magazine Electrical World, where he discussed the possibility of permanent magnetic impressions for recording sound and suggested, as a medium, cotton or silk thread, in which steel dust was suspended. Smith also considered steel wire but didn't think it would be possible to establish a magnetic pattern as a replica of currents produced by a microphone. Smith never built a machine or proved his theory practically.