Pressure-flow characteristics of /m/ and /p/ production in speakers without cleft palate: developmental findings.

OBJECTIVE: The purpose of this study was to describe the pressure-flow characteristics of a large sample of speakers without cleft palate ranging in age from early childhood to young adulthood.
METHOD: Speakers consisted of 223 children, teens, and adults without cleft palate categorized into five age groups: 6 through 8 years, 9 through 10, 11 through 12, 13 through 16, and 18 through 37 years. Speakers produced the syllables /mi/, /pi/, and /p/¿/, the word "hamper," and the sentence "Peep into the hamper." The pressure-flow method was used to determine oral air pressure, nasal airflow, and estimates of velopharyngeal (VP) orifice size associated with /ml and /p/ production. Descriptive statistics were computed for each age group and speech sample. Analysis of variance (ANOVA) procedures were used to determine the effects of age, sex, and production level (word versus sentence) on the aerodynamic variables.
RESULTS: ANOVA procedures indicated significant main effects (p < .01) of age on most of the aerodynamic variables during production of /m/ and /p/. No significant main effects or interactions involving sex were found for any variable. Regardless of age, approximately 95% to 99% of the speakers exhibited airtight VP closure during /p/ at syllable level, depending upon the selected nasal airflow criterion. ANOVA procedures also indicated significant main effects of production level (word versus sentence) on each of the aerodynamic variables during the /mp/ sequence. These effects appeared to be related to speaking rate.
CONCLUSIONS: The study suggests that speakers without cleft palate exhibit essentially complete VP closure during production of oral pressure consonants in isolated syllables, and developmental aspects of speech aerodynamics be considered during pressure-flow testing.