Speaking-trumpet,

Speaking-trumpet, an instrument for enabling the sound of the human voice to be conveyed to a greater distance. It is of the utmost use on shipboard in enabling the officers to convey orders during windy weather from one part of the deck to another, or to the rigging. The invention is ascribed to Sir Samuel Morland, in 1670, though Athanasius Kircher laid claim to it. Morland's trumpet was of the same form as that now in use—viz. a truncated cone, with an outward curve or lip at the opening. The theory of the action of this instrument is much the same as that of the sounding-board of a musical instrument, but the sounding-board is aerial instead of solid. The air immediately in front of the instrument is acted upon over so wide a surface that it cannot effectively evade compression and rarefaction by any process of overflow and inflow towards the sides, and the result is as if the air were well laid hold of and firmly set in vibration.