On March 7, 1876, the U.S. Patent Office granted him Patent Number 174,465 covering, the method of, and apparatus for, transmitting vocal or other sounds telegraphically . . . by causing electrical undulations, similar in form to the vibrations of the air accompanying the said vocal or other sounds.' After inventing the telephone, Bell continued his experiments in communication, which culminated in the invention of the photophone-transmission of sound on a beam of light--a precursor of today's optical fiber systems. He also worked in medical research and invented techniques for teaching speech to the deaf. The range of Bell's inventive genius is represented only in part by the 18 patents granted in his name alone and the 12 he shared with his collaborators. These included 14 for the telephone and telegraph, four for the photophone, one for the phonograph, five for aerial vehicles, four for hydroairplanes, and two for a selenium cell. In 1888 he founded the National Geographic Society.
He came up with the term "Bel" as the name of the measure of loudness of a sound, naming it after himself. The bel is so coarse a measure that the tenth of a bel, or decibel is what is commonly used. See Acoustics for technical information.