 The word "acoustic" comes from the Greek "akoustikos" meaning hearing, as with hearing of sound waves in air.Acoustic telegraphy devices were electromechanical and made musical or buzzing or humming sound waves in air for a few feet.But the primary function of these devices was not to generate sound waves, but rather to generate alternating electrical currents at selected audio frequencies in wires which transmitted telegraphic messages electrically over long distances.