Intraspeaker variability in vowel production: An investigation of motherese, hyperspeech, and Lombard speech in Jamaican speakers

Examination of five acoustic parameters (F0, F1, F2, segmental duration, and intensity) allowed comparison of Infant-Directed Speech (IDS), Hyperspeech, and the Lombard reflex. These phenomena have typically been investigated separately, each characterized in terms of one or two acoustic features (e.g., intensity for Lombard speech). The present two-part experiment examined intraspeaker and interspeaker variability in speakers of Jamaican Creole and Jamaican English. IDS and Lombard speech showed similar adjustments in two parameters (F0 and intensity), and IDS and Citation speech showed the greatest spectral differences. This result is important because it shows that while one or two acoustic parameters may be crucial characteristics of a type of exaggerated speech, task production involved the systematic adjustment of a complex set of continuous acoustic parameters. Taken together, the acoustic outcomes for the types of perturbations investigated here allow the tasks to be arranged along a continuum. These adjustments resemble patterns associated with the manipulation of sociolinguistic markers reported in sociophonetic studies of “style-shifting.” We argue that the two phenomena may be treated under a unified account of intraspeaker variability that builds upon the sociolinguistic concept of Audience Design.