A review of research on speech intelligibility and correlations with acoustic features

This review article provides an overview of differences between conversational (or cnv) and clear (or clr) speech, for a variety of speakers, in terms of speech intelligibility, and in terms of acoustic characteristics. Researchers have studied the relationship between acoustic features and speech intelligibility by, for example, studying correlations. However, the question “which acoustic features of clr speech cause it to be more intelligible” is still unanswered. To approach this question, it is valuable to summarize past findings related to speech intelligibility and their relationship with acoustic features, while not being limited to a review of only clr speech materials. The outcome of this review can then be applied to restrict the search space in the process of finding acoustic features that contribute to increased speech intelligibility. Finally, we review computer-processing techniques to improve speech intelligibility, summarize these findings, and propose future modifications. Keyword: speech intelligibility, clear speech, speech modification, elderly listeners