Ear Phonautograph (Reconstruction)
This instrument is a reconstruction of Alexander Graham Bell and Clarence J. Blake’s ear phonautograph: an 1874 curiosity that used an excised human middle ear to visually inscribe sound waves. Originally conceived of as a tool for deaf education, it became better known for providing Bell with the technical insights he needed to develop and patent the telephone. The reconstruction was made in 2017 an effort to better understand the design, fabrication, and broader significance of the original 1874 instrument, which is today believed lost to history. The reconstruction is in the permanent collection of Ingenium - Canada's Museums of Science & Innovation and is currently on display at the Canada Science & Technology Museum in Ottawa, Canada.
Functionally, the 1874 ear phonautograph worked by channelling sound wave vibrations, produced by speaking into the mouthpiece of the instrument, into the auditory canal of a human middle ear. This in turn caused a stylus, attached to the ear drum’s ossicle bones, to similarly vibrate. When a plate of glass – smoked with soot from an oil lamp – was pulled quickly underneath the stylus, the speech vibrations were etched as a continuous waveform across its surface. This etching could then be ‘read’ by the speaker to determine the shape or pattern that the speech vibrations produced.
The ear phonautograph was inspired by Édouard-Léon Scott de Martinville’s original phonautograph, or sound-writer, first introduced in 1857. Scott de Martinville felt that an instrument that "would reproduce by a graphic trace the most delicate details of the motion of the sound waves" ( Scott de Martinville, 1857: trans. by Feaster, 2010, p 7 ) could contribute greatly to the preservation and scientific study of sound. For several years, Scott de Martinville experimented with natural materials like goldbeater’s skin and boxwood to best approximate the human ear drum (tympanic membrane) and ossicle bones.
What made Bell and Blake’s instrument unique is that it went a step further by using an actual human ear as the tympanic mechanism at the centre of the instrument. They felt that the sensitivity of a biological ear would enable their phonautograph to respond even more accurately to sound wave vibrations, and thereby produce more precise visual sound etchings, than was previously possible. This improvement was desirable for a project Bell was working on with his father at the time called 'visible speech,' which involved – controversially – employing various visualisation techniques to teach the deaf how to speak. Bell felt that a more precise sound-writing instrument would allow his deaf students to clearly see what certain vowels 'sounded' like, and thereby improve the clarity of their speech by comparing a hearing person’s etchings to the etchings they themselves produced by speaking into the machine.
The ear phonautograph ultimately failed to perform adequately for this purpose, and was soon abandoned by Bell; however, it did have an important role to play in his other scientific and commercial pursuits. As Bell claimed in the years following his successful telephone patent application in 1876, it was in studying the relationship between the tympanic membrane and ossicle bones in the ear phonautograph that he gained the technical insight he required to invent the telephone in 1876. "While engaged in these [ear phonautograph] experiments," he wrote in 1877, "I was struck with the remarkable disproportion in weight between the membrane and the bones that were vibrated by it. It occurred to me that if a membrane as thin as tissue paper could control the vibration of bones that were, compared to it, of immense size and weight, why should not a larger and thicker membrane be able to vibrate a piece of iron in front of an electro-magnet" ( Bell, 1877, p 406 ).
For a detailed account of the building of this reconstruction – including additional historical information, scholarly sources, photographs, and research outcomes – see: http://journal.sciencemuseum.ac.uk/browse/issue-12/writing-sound-with-a-human-ear/