ArticleThompson AE, Hixon TJ.
Cleft Palate J. 1979 Oct;16(4):412-20.
Nasal air flow was measured during the speech of 112 normal subjects (59 females and 53 males) ranging in age from three years to 37 years, six months. Flow was zero during nearly all oral consonant and vowel utterances, suggesting that velopharyngeal closure was air-tight. Flow occurred during all nasal consonants and during vowels adjacent to nasal consonants. These effects were interpreted as showing that progressively older subjects and female subjects demonstrate earlier anticipatory coarticulation in preparation for forthcoming nasal consonants.