The phonetics of post-nasal voicing

Many of the world’s languages display a phonetic pattern whereby obstruents appear as voiced when following a nasal consonant. This article proposes a phonetic mechanism that favors postnasal voicing. The mechanism is based on two effects, which sometimes reinforce, and sometimes contradict each another. One effect is “nasal leak, ” the leakage of air through a nearly closed velar port during the coarticulatory period between an oral and a nasal segment. The other is “velar pumping, ” which arises from the vertical motion of a closed velum. The main purpose of the article is to test this proposal, in two ways. First, a computational simulation of vocal tract aerodynamics is used to show that, under a range of plausible assumptions, the mechanisms posited would indeed produce a substantial phonetic effect in the direction of postnasal voicing. Second, measurements were carried out of the productions of 5 native speakers of English producing stops in a controlled comparison context (postnasal / [ tam__ _ ¡ ] vs. / postoral [ ta ¢ ___p ¡]). The results indicate that postnasal voicing present as a quantitative effect even in a language whose phonology lacks a qualitative postnasal voicing process. 1