Acoustic correlates of English and French nasalized vowels

Acoustic analysis of nasalized vowels in the frequency domain indicates the presence of extra peaks: one between the first two formants with amplitude P1 and one at lower frequencies, often below the first formant, with amplitude P0. The first-formant amplitude A1 is also reduced relative to its amplitude for an oral vowel. These acoustic characteristics can be explained by speech production theory. The objective of this study was to determine the values for the acoustic correlates A1-P1 and A1-P0 (dB) for quantifying nasalization. They were tested as measures of nasalization by comparing vowels between nasal consonants and those between stop consonants for English speakers. Also, portions of nasal vowels following a stop consonant were compared for speakers of French, which makes a linguistic distinction between oral and nasal vowels. In the analysis of English, the mean difference of A1-P1 measured in oral vowels and nasalized vowels had a range of 10 dB-15 dB; the difference of A1-P0 had a range of 6 dB-8 dB. In the study of French, the difference of A1-P1 measured between the least-nasalized portion and the most-nasalized portion of the vowel had a range of 9 dB-12 dB; for A1-P0, the difference ranged between 3 dB and 9 dB. In order to obtain an absolute acoustic measure of nasalization that was independent of vowel type, normalized parameters were calculated by adjusting for the influence of the vowel formant frequencies.