American English diphthong transitions and the acoustic vowel space: A pilot comparison of two tasks

Abstract

The purpose of the present study is to evaluate the potential relationship(s) between diphthong transitions and the acoustic vowel space parameters in two speaking tasks. Diphthongs are associated with acoustic changes that reflect changes in vocal tract configurations, affording unique opportunities for investigating the articulatory-acoustic link. The acoustic vowel space, a representation of monophthong vowels in a two-dimensional plane defined by the first and second formant frequencies (F1 and F2), has been widely used to interpret articulatory-acoustic consequences and to index articulatory integrity. Nevertheless, limited is known as to how diphthongs and monophthong vowels account for the acoustic working space together [Lee et al., JASA 136(4), 1880–1894 (2014)]. To add to this inquiry, transitions of American English diphthongs /ei/, /ɑɪ/, /ɑʊ/, /oʊ/, and /ɔi/, defined by the primary F2 transition, are examined with respect to the quadrilateral vowel space anchored by /i/, /æ/, /ɑ/, and /u/. The speech sounds were obtained from four male speakers in two tasks, sentence reading and connected speech, that have been shown to elicit vowel space changes. It is hypothesized that greater diphthong transitions are associated with parameters corresponding to a larger vowel space. Findings will be discussed within the framework of the acoustic theory.