Coarticulation effects on the nasalization of vowels using nasal/voice amplitude ratio instrumentation.

Nasal coarticulation in phonetically controlled nonsense syllables was investigated in four normal adult speakers. Nasalization was determined using the ratio of a nasal accelerometer signal amplitude to airborn microphone signal amplitude. Measurements of nasalization were made at the midpoint of vowels and at a constant time from the nasal consonant. Nasal acoustical coupling was greater for high vowels than for low vowels in all consonant contexts. Nasalization was also greater for vowels between two nasal consonants than for vowels between a nasal consonant and a fricative or stop. Results for progressive versus regressive assimilation depended on the measurement strategy. For within-vowel measurements made a constant time from the nasal consonant, prenasal vowels showed greater nasalization than postnasal vowels. This nasal accelerometric technique shows promise for clinical assessment of articulatory details of velar function.