Perceptual and acoustic aspects of lexical vowel reduction, a sound change in progress

Abstract

In the present study 20 Dutch male speakers were asked to read aloud 47 test words in a word list and in short sentences. Part of this word set was also named by them through the presentation of pictures. A group of 20 listeners was asked to identify an unstressed vowel in all of these test words. The vowel responses of listeners were recoded into two broad categories: “full vowel” and “schwa”. Our aims were (1) to find out to what extent listeners are able to unambiguously distinguish between these two categories, (2) to investigate the influence of the frequency of occurrence of words on the classification of the test vowels, (3) to investigate the influence of speaking styles on the classification of the test vowels by comparing the speech conditions “word list”, “pictures” and “sentences”. The experimental results showed that (1) listeners often could not unambiguously classify the test vowels, especially if these occurred in interstress position, (2) the number of schwa responses was much higher for vowels in words with a relatively high frequency of occurrence, (3) the number of schwa responses increased in a more casual speaking style. Acoustic measurements on the test vowels revealed a clear relation between the perceptual results and the acoustic features of the vowels. Although the preconditions for the sound change “full vowel → schwa” in several Dutch words are excellent, the actual completion of the sound change is in our view to a large extent blocked by the rather close correspondence between Dutch vowel sounds and their orthographic representations.