Phonetic Contexts: Their Effects on Perceived Nasality in Cleft Palate Speakers

Abstract

Among the factors found related to cleft palate speech by a number of investigators, those dealing with the phonemic distinction of nasalized/ non—nasalized appears as one of the major speech problems of cleft palate speakers. A consistent trend in the literature has revealed the articulatory ' skills of cleft palate speakers to be influenced to a considerable degree by the presence of perceived nasality (2, 4, 8, 9, 12, 14, 15, I6, 17, 19). Phonetic contexts have also been shown to influence the perceived defectiveness of phonemes in cleft palate speakers (11, 18). Carney and Sherman (3) demonstrated that isolated vowels, isolated CVC syllables, and CVO syllables in a connected speech passage were judged as more nasal on high vowels than on low vowels for cleft palate speakers. These findings appear to be commensurate with the finding that misarticulations are inconsistent in cleft palate speakers. The inconsistent misarticulations may thus be a function of the phonetic context in which the phoneme is tested since nasal distortion may influence judgements of articulatory defectiveness. Other factors related to cleft palate speech are those of intraoral breath pressure and air flow. Phonemes requiring greater intraoral breath pressure and air flow (1, '7) are preceived as being more defective than others (6). The most likely explanation for the occurrence of greater degrees of nasality is that some consonants in conjunction with high vowels make greater demands upon the valving function, i.e., higher points of posterior pharyngeal wall/velar contacts, tighter velopharyngeal seals, and greater velar excursion.