Invention of the telephone
The carbon microphone was independently developed around 1878 by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, and most historians credit him with its invention.
Théâtrophone
The origin of the théâtrophone can be traced to a telephonic transmission system demonstrated by Clément Ader at the 1881 World Expo in Paris. The system was inaugurated by the French President Jules Grévy, and allowed broadcasting of concerts or plays. Ader had arranged 80 telephone transmitters across the front of a stage to create a form of binaural stereophonic sound. It was the first two-channel audio system, and consisted of a series of telephone transmitters connected from the stage of the Paris Opera to a suite of rooms at the Paris Electrical Exhibition, where the visitors could hear Comédie-Française and opera performances in stereo using two headphones; the Opera was located more than two kilometers away from the venue. In a note dated 11 November 1881, Victor Hugo describes his first experience of théâtrophone as pleasant.