He talks about making a set of references values for vowels in this video. This is something I had thought of too in the past, but limited in scope of teaching

He talks about making a set of references values for vowels in this video. This is something I had thought of too in the past, but limited in scope of teaching English to Japanese native speakers. It struck me that instead of teaching to target prononciations of words using the whole vowel space of american or British English, which has some differences that are hard to understand for native Japanese speakers, a vowel space could be made that was optimized listener understandability, but having enough differentiation of sounds, and ease of articulation.