Horn-type electrothermal loudspeakers

As an alternative to conventional electromechanical loudspeakers, an attempt is made to utilize an electrothermal process for sound reproduction. A brief history of gaseous loudspeakers is presented, with emphasis on the discovery of the sound-generating ability of a seeded gas flame modulated by an electrical audio input. The theory and basic design requirements are discussed for a horn-type loudspeaker in which the flame is enclosed in a cylindrical tube. Two such experimental loudspeakers, one constructed for public address applications and the other for high-frequency reproduction, are described. A complete evaluation of these loudspeakers, including frequency response, signal-to-noise ratio, durability, and feasibility, is also carried out.