Starting in 1955, when he was appointed at the University of Grenoble, Gsell undertook to develop its Institute of Phonetics into an internationally recognized laboratory.
Gsell was appointed General Secretary of the Permanent Council for the Organization of International Congresses of Phonetic Sciences in 1961.
In the iconoclastic fever of the May 1968 events in France, Gsell was criticized as a representative of old-style, retrograde scholarship and had to discontinue his teaching in Grenoble.
In addition to classical languages such as Greek, Latin, Sanskrit and Old Persian, he knew Old Norse and Gothic.
He also knew Thai (Siamese) and acquired some first-hand knowledge of a considerable range of languages.