Speaker and production characteristics of posterior nasal fricatives

Abstract

Posterior nasal fricatives (PNF) are unusual articulations produced by children both with and without velopharyngeal (VP) anomalies to replace oral fricatives. PNFs are produced by occluding the oral cavity and forcing airflow through a partially closed VP port to create turbulent noise. Often, extra noises occur due to displacement of mucous and/or tissue flutter. The headset of the nasometer was used to record the separate oral and nasal acoustic signals from 18 children who produced PNFs. They ranged in age from 4 to 15 years, 11 were males, and 11 had some form of cleft palate. Examination of the oral acoustic waveforms revealed that all children produced a stop gesture during intended fricative targets—typically a lingual-alveolar or palatal articulation. Sixteen of the children produced a clear flutter (raspberry-like) noise as evidenced by quasi-periodic components in the nasal spectra. All children used PNFs to replace /s/, 13 (72%) to replace /z/, 12 (67%) to replace /tʃ/, and 6 (33%) to replace /ʃ/ and /dʒ/. Most of the children had known histories of conductive hearing loss. Most of the children with cleft palate had adequate VP closure during stop consonant production. Possible causes of PNFs are discussed.