At BAAP last week there was a showing of “Highlights from the UCL Phonetics Film Collection”. As Michael Ashby explained, when the UCL Department of Phonetics moved out of 21 Gordon Square a few years ago he discovered that they had accumulated about 12,000 feet of movie film spanning the years from the early 1920s to the 1970s. Much of this footage is rare or even unique. He is now in the process of researching and restoring the material, as finances allow.
Several of the clips he showed us were x-ray sound films of short stretches of speech, taken during the window of time between the technical advances that made it possible to carry out cineradiography and the realization that exposure to the high doses of radiation involved carried serious health risks for the person being filmed.
Films made by Ken Stevens at Haskins are relatively well known (you can watch one on YouTube here).
But I was unaware of the film made by Paul Menzerath and Robert Janker in Bonn and shown at the second International Congress of Phonetic Sciences in London in 1935. This was the first x-ray sound film and, Michael thinks, probably the first to achieve slow motion. There is one other copy known to be extant. You can watch it here (where however the date is wrongly given as 1937 and Menzerath is not mentioned). As the speaker says, “besonderes Interesse verdient vor allem die Wiedergabe der Sprache” [most of all, the reproduction of speech is of particular interest].