Alexander Graham Bell credited with being the first person to invent the telephone was interested in the study of acoustics since childhood. His own mother was deaf and later in life his wife was deaf too. All this contributed in furthering his interest in the science of speech and sounds, he taught deaf children using his father's technique of Visible Speech that combined its visual aspects as a symbol for actual speech.
Bell was always interested in electricity and believed that it could transmit human speech; he once experimented by playing a piano and transmitting the music by means of wires. Thomas Watson a repair mechanic became his assistant and helped him in resolving the mechanical part of his invention by building machines according to the designs of Bell. Thus it was on 10 March 1876 that for the first time in history human speech was propagated when Bell's assistant Watson heard his words in the next room, 'Mr. Watson, Come here, I want you' on one of their machines.