In the late 19th century there was an explosion in the development of electrical apparatus, particularly related to the telephone. Some of these inventions would have implications for the eventual development of ‘assistive devices’ for deaf people, what we could call hearing aids.
François Dussaud (1870-1953) was a Swiss-born inventor, from Stäfa near Zurich (note he is also claimed for Geneva). His father Bernard was a School Inspector. He studied under the biologist Emile Yung, and was clearly talented, becoming a Phd in 1892. He became Privatdozent at the University of Geneva in 1894.
A couple of years later he moved to Paris, and had what seems like a golden period of invention. Dussaud worked on sound and light, and his first invention was the ‘Microphonograph,‘ followed by the ‘Teleoscope‘ and the ‘Multiphone.’
In January 1896, Dussaud was inspired by “the fate of an unfortunate deaf mute” and he
resumed a study that he had begun some time before, and applied his efforts to the finding of an apparatus that should increase the intensity of sound at will. After a year of research, he, on the 29th of December last, operated with entire success, before a certain number of physicians, in the laboratory of physiology of the Sorbonne, the instrument to which he has given the name mentioned above. The amplification of sounds seemed extraordinary, and on the next day Dr. Laborde, superintendent of the laboratory of physiology, presented to his colleagues of the Academy of Medicine the result of the observations that he had made with the apparatus under consideration.
The microphonograph consists of two parts, a registering apparatus and a repeater.
The Registering Appantus,—This consists [see above figure] of a horizontal cylinder actuated by clockwork. Upon this cylinder is fixed a wax roller in front of which a piece of the size and shape of a watch is moved through a mechanism. This piece is formed essentially of small electromagnets that act upon a disk which controls the tool that is designated to engrave the wax. For registering feeble sounds, there is placed in the region corresponding to the organ to be examined a microphone of a peculiar system, that is connected with the microphonograph registering apparatus by an electric current, derived from 1 to 60 small sulphate of mercury elements. Through the intermedium of this current, the sounds collected by the microphone are faithfully repeated by the disk of the microphonograph and inscribed upon the wax by the graver. (The Phonoscope, June 1897, p.10)
Another article explains,
EDISON tells us that he will shortly be able to make the blind see by means of the X rays. Meanwhile, Professor Dussaud, of the University of Geneva, has invented an apparatus to enable the deaf to hear. The microphonograph he has just issued to the world magnifies the human voice in the same way as a lens magnifies a picture. It is simply a telephone connected electrically with a phonograph, but a far more sensitive phonograph than Edison’s ordinary model. There is, of course, an electric battery, sulphate of mercury being used, and from one cell to sixty cells, according to the degree of deafness of the person. Of course, the apparatus is useless in case of absolute deafness ; but, fortunately, such an infirmity is far rarer than is suspected. Ninety-five per cent of so-called stone-deaf persons can be made to hear and understand by means of Professor Dussaud’s invention. How ? You speak into the phonograph. You make it repeat your words, which are transmitted by a sort of microphone and speaking tube into the deaf ear. Professor Dussaud, in the same order of ideas, is preparing for the 1900 exhibition an apparatus which will enable 10,000 people, who may be all deaf, to follow a lecture. (The Charities Review)
The American Annals of the Deaf, explored the use of the Microphonograph for Deaf education, in a series of articles.
This French website, Phonorama, has a nice photograph of Dussaud in his laboratory at the Sorbonne, and a photograph that the engraving above must owe something to. This engraving illustrates Dussaud and a young Deaf boy, with the ‘ah!’ moment, for want of a better term, that is sometimes depicted in video clips of people who have cochlear implants turned on for the first time.
He produced other inventions, worked for Pathé for a while, and he also pioneered a way of playing sound with film. During the First World War he worked as a scientific assistant on the war effort. Dussaud spent the Second World War in Switzerland, and died in Paris in 1953.
The Microphonograph, British Deaf Monthly, 1898, p.148-9
H. Marichelle, The use of the Microphonograph in the education of the deaf. —I American Annals of the Deaf, Vol. Vol. 45, No. 6 (OCTOBER, 1900), pp. 495-503
H. Marichelle, The use of the Microphonograph in the education of the deaf. —II American Annals of the Deaf, Vol. 46, No. 1 (JANUARY, 1901), pp. 24-38
H. Marichelle, The use of the Microphonograph in the education of the deaf. —III American Annals of the Deaf, Vol. 46, No. 2 (MARCH, 1901), pp. 149-158
Ladreit de Lacharrière, The Dussaud Microphonograph, American Annals of the Deaf, Vol. 44, No. 1 (JANUARY, 1899), pp. 28-32