Vowel Inherent Spectral Change in the Vowels of North American English

Abstract

Nearey and Assmann (1986) coined the term ‘vowel inherent spectral change’ (VISC) to refer to change in spectral properties inherent to the phonetic specification of vowels. Although such change includes the relatively large formant changes associated with acknowledged diphthongs, the term was explicitly intended to include reliable (but possibly more subtle) spectral change associated with vowel categories of North American English typically regarded as monophthongs. This chapter reviews statistical and graphical evidence of dynamic formant patterns in vowels of several CV and CVC syllable types in three regional dialects of English: Dallas, Texas (Assmann and Katz, 2000), Western Michigan (Hillenbrand et al., 1995) and Northern Alberta (Thomson 2007). Evidence is reviewed for the importance of VISC in vowel perception. While certain apparent VISC patterns show up across dialects, both dialect differences and differences in context make it clear that more sophisticated methods will be required to fully separate several factors affecting formant change in vowels. Promising preliminary results are presented using a new non-linear regression method that extends compositional models of Broad and Clermont (1987, 2002, 2010) to include dual vowel targets.