How to put one person's tongue inside another person's mouth
Peter Ladefoged · The Journal of the Acoustical Society of America · 1976
An algorithm has been devided for recovering the shapes of the tongue involved in producing different vowels simply from a knowledge of the first three formant frequencies. The calculated tongue shapes may then be displayed inside a standard vocal tract shape. The algorithm has been tested by recovering the tongue shapes of a wide variety of vowels spoken by a number of different speakers and comparing them with the original x rays. The exact shapes of low vowels, such as [æ, α] are not recovered as accurately as those of other vowels, but the reconstructed tongue shapes of most men can be fitted very appropriately into a standardized diagram of the organs of speech based on x rays of the author (Peter Ladefoged). There is inevitably some distortion of the organs when a woman's tongue is put inside the author's mouth, because of the notable anatomical differences between men and women. The algorithm gives good approximations even when applied to speakers of other languages, such a Russian, Japanese, and Ngwe.