The Aeroacoustics of Nasalized Fricatives

Understanding the relationship of aerodynamic laws to the unique geometry of the human vocal tract allows us to make phonological and typological predictions about speech sounds typified by particular aerodynamic regimes. Some have argued that the realization of nasalized fricatives is improbable because fricatives and nasals have antagonistic aerodynamic specifications. Fricatives require high pressure behind the supralaryngeal constriction as a precondition for high particle velocity. Nasalization, on the other hand, vents back pressure by allowing air to escape through the velopharyngeal orifice. This implies that an open velopharyngeal port will reduce oral particle velocity, thereby extinguishing frication. By using a mechanical model of the vocal tract and spoken fricatives that have undergone coarticulatory nasalization, it is shown that nasalization must alter the spectral characteristics of fricatives. It is hypothesized that nasalization generally has a deleterious effect on the acoustic distinctiveness of fricatives, explaining the typological rarity of nasalized fricatives.