By close, they mean (from the article): > Everywhere this word appears to be a simple syllable with a low-front central vowel, glottal onset consonant if any,

By close, they mean (from the article): > Everywhere this word appears to be a simple syllable with a low-front central vowel, glottal onset consonant if any, and questioning intonation. My wife's parents have a similar thing in English as an aside. `Huh` indicates that they've heard something novel, `huh?` indicates that they didn't hear you.