Applying refined automatic formant measurement to determination of the orientations of vowel distributions

Abstract

In order to remedy recurrent problems with false formant readings obtained with an automatic formant measurement routine, prototype-based automatic measurements were compared with manual formant measurements of the same uttered vowels. Two refinements that avoided false formants, one involving the option to skip measured formant racks and the other involving an expectation that successive formants would show successively lower amplitudes, were developed. This method was then applied to seven corpora representing diverse English dialects, with satisfactory results. The measurements of each vowel thus obtained were then subjected to principle component analysis to determine the orientation of the tokens in F1/F2 space. Most vowels exhibited distributions that apparently reflect degree of jaw opening. However, /u/ in North American varieties (with pre-/l/ and post-/j/ tokens excluded) showed mostly horizontal orientations, even when post-coronal and non-post-coronal tokens were considered separately. This pattern contrasted sharply with the vertical orientations of mid back vowels. /u/ was also the only vowel whose orientations coincided consistently with ongoing changes in the communities. We hypothesize that the factors responsible for the horizontal orientations of /u/ also lie behind its cross-linguistic tendency to shift frontward. In order to remedy recurrent problems with false formant readings obtained with an automatic formant measurement routine, prototype-based automatic measurements were compared with manual formant measurements of the same uttered vowels. Two refinements that avoided false formants, one involving the option to skip measured formant racks and the other involving an expectation that successive formants would show successively lower amplitudes, were developed. This method was then applied to seven corpora representing diverse English dialects, with satisfactory results. The measurements of each vowel thus obtained were then subjected to principle component analysis to determine the orientation of the tokens in F1/F2 space. Most vowels exhibited distributions that apparently reflect degree of jaw opening. However, /u/ in North American varieties (with pre-/l/ and post-/j/ tokens excluded) showed mostly horizontal orientations, even when post-coronal and non-post-coronal tokens were considered separately. This pa...