Hearing. Spent much of his life in Germany, where he published Alphabeti vere Naturalis Hebraici Brevissima Delineatio [A Brief Description of the Truly Natural Hebrew Alphabet]. This eccentric and mystical work claimed that the Hebrew language was the only "natural" language of humans, and that each Hebrew character represented the various positions of the vocal organs necessary to pronounce that sound. From this theory van Helmont devised a method for teaching the deaf to speak, and claimed to have taught one deaf person to speak within just 3 weeks.
Arnold on the Education of the Deaf, p.23-24.