In a previous study, Arai implemented a sliding vocal-tract model based on Fant's three-tube model and demonstrated its usefulness for education in acoustics and speech science. The sliding vocal-tract model consists of a long outer cylinder and a short inner cylinder, which simulates tongue constriction in the vocal tract. This model can produce different vowels by sliding the inner cylinder and changing the degree of constriction. In this study, we investigated the model's coverage of vowels on the vowel space and explored its application for vowel production in the speech and hearing sciences.