Reanalysis of Vowel Formants in the Buckeye Corpus

Vowel formants are an important piece of information for mapping acoustic signals to a specific position in a vowel space defined by cardinal vowels. Each formant of a vowel can be obtained by averaging multiple formant values calculated from sliding analysis windows applied over the signals in the vowel area or simply by taking the formant value at a time point. Depending on which part of the vowel span is used, the formant values can change and as a result its position in the vowel space can also change. Vowels in a large corpus of spontaneous speech can be affected by various uncontrolled factors, which brings about large deviations in formants. In particular, when averaging multiple values from a token, the internal variation in each vowel token is easily ignored. This paper shows that internal variations can affect the final results of the vowel formants that represent a specific vowel type. This is particularly the case with the first formant of non-low vowels which tends to be more affected than with low vowels.