I. On the pneumatic action which accompanies the articulation of sounds by the human voice, as exhibited by a recording instrument
William Henry Barlow · Proceedings of the Royal Society of London · 1874
Abstract All articulated sounds made by the human voice are accompanied by the expulsion of air from the mouth ; and in a series of articulated sounds the air is ejected in impulses which vary in quantity and pressure, and in the degree of suddenness with which they commence and terminate. It appeared to me that it would be interesting and probably useful, as tending to elucidate the process and effects of articulation, to construct an instrument which should record these pneumatic actions by diagrams, in a manner analogous to that in which the indicator-diagram of a steam-engine records the action of the engine.