What *can* make clear speech clear: Lessons learned from the Ferguson Clear Speech Database

Abstract

Extensive acoustic and perceptual analyses have been carried out on the materials from the Ferguson Clear Speech Database (FCSD), which was recorded at Indiana University in 2002. The FCSD consists of 41 untrained talkers reading 188 sentences under instructions first to speak in a manner “as much like your normal conversational style as possible” and later to “speak clearly, so that a hearing-impaired person would be able to understand you.” My intent in developing the FCSD was to exploit the expected wide acoustic and perceptual variability among the talkers and use a talker-differences approach to answer the question, “What makes clear speech clear?” In this presentation, I will summarize data from studies of vowel intelligibility, word intelligibility, and perceived sentence clarity along with global and fine-grained acoustic analyses, and discuss how all of these measures are related across the 41 talkers. My hope is that this birds-eye view of the FCSD data will reveal subgroups of talkers in which the talkers adopted certain “profiles” of clear speech acoustic changes that yielded specific helpful perceptual changes. If time permits, I will also review data on perceived talker indexical properties and how they change when talkers speak clearly.