Diaphone (fog horn)
The diaphone is a compressed air operated fog horn .
The diaphone is based on the movement of a slotted piston in a cylinder and was patented in 1903 (1910 according to other sources) by the mechanic and inventor John Pell Northey , professor at the University of Toronto . It is based on a sound generator developed by Robert Hope-Jones , a British electrician and organist who emigrated to America. This consists of a plate which, like the membrane in a membrane pipe, periodically opens and closes an air passage and thus generates an air oscillation in the downstream tube. According to the type of sound generation, the diaphone is assigned to the group of retreating reeds , a term that Hope-Jones himself introduced. It is also the basis for the famous Wurlitzer organ .
The diaphone produces a main tone of typically around 250 Hz . When the tone generation is switched off, the device still sounds a little, but at a lower frequency of around 100 to 150 Hz. This leads to the typical "grunt" of the diaphone. Under certain circumstances, this grunt can be heard further than the main tone due to the lower frequency.
The first diaphone was installed in Buffalo, New York State, in 1914 to improve safety for shipping on the Great Lakes .
In addition to their function as fog horns, diaphones were and are also used to generate alarm signals in cities.
Web links
- Jeff Laser: The Diaphone Fog Signal . Terry Pepper, 2007
- GameWellDiaphone with video and sound clips
Individual evidence
- ^ Francis W. Galpin: The Whistles and Reed Instruments of the American Indians of the North-West Coast . In: Proceedings of the Musical Association, 29th Session, 1902-1903, pp. 115-138, here p. 127