Fant [G. Fant, Acoustic Theory of Speech Production (Mouton, The Hague, 1960)] has been the first to use the four‐tube model of the vocal tract and to introduce vocalic nomograms to speech production studies. These nomograms proved to be an efficient tool for the study of articulatory–acoustic relationships. This paper deals with particular regions of these nomograms, referred to as focal points. These are points where formant convergences occur and where affiliations between formants and cavities are exchanged. A study of appropriate nonsense words has confirmed the existence of these points in natural speech. Generating nomograms with an articulatory model of the vocal tract allowed the location of these convergence regions along the vocal tract, and demonstrated that vowels [i,a,u,y] are located in the vicinity of focal points. The examination of the human speakers’ nomograms obtained by Ladefoged and Bladon from real speaker productions [P. Ladefoged and R. A. W. Bladon, Speech Commun. 1, 185–198 (198...