- Laurence Libin
Pneumatic-mechanical device for amplifying sound outdoors and in large indoor spaces. It was patented in England in 1898 and 1901 by the aviation engineer and acoustician Horace Short (1872–1917) and developed (initially as a hobby) from 1903 by the mechanical engineer and inventor Sir Charles Algernon Parsons (1851–1931), who had purchased the patents. It was intended for use with gramophones and was also applied to instruments for live performance, like the earlier diaphragm and horn amplification system of Augustus Stroh. As applied to the gramophone, the auxeto modulates a flow of compressed air by means of a grid-valve (a reed assembly operating somewhat like the reeds of a harmonica). As the needle moves along the record groove, a metal comb affixed to the stylus bar opens or closes slots in the valve seat, imparting powerful pulses of air corresponding to the sounds originally recorded; these sound pulses are then projected through a large horn. The air compressor, which feeds a cylindrical pressure tank, is driven by an electric motor, and the air is filtered to remove particles that might clog the valve. When less volume is required or no electricity is available, a so-called soundbox can be substituted for the auxeto, allowing the gramophone to operate normally....