Project Summary
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Project Summary
Background and Objectives
A research project is proposed to investigate how human listeners process speaker variability in
speech perception. Speech perception is the process by which a listener interprets the sounds produced by
a speaker in order to understand a spoken message. Acoustic-phonetic research over several decades has
shown that the same spoken message can vary significantly across speakers. However, listeners are able
to understand sounds and words spoken by different speakers. How listeners achieve such perceptual
constancy despite speaker variability is a foundational issue in speech perception. Research on speaker
variability has traditionally focused on segmental features (consonants and vowels) in the English
language. By contrast, the effect of speaker variability on processing suprasegmental features (e.g., lexical
tones) in non-English languages is largely unknown. To fill this gap, the proposed project will
investigate the processing of speaker variability in tone languages. In tone languages, lexical tones are
functionally equivalent to consonants and vowels. The primary acoustic correlate of lexical tone is
fundamental frequency (F0). Because F0 range varies across speakers, a phonologically high tone
produced by one speaker could be acoustically equivalent to a phonologically low tone produced by
another speaker. Conversely, a given tone produced by two speakers could be acoustically distinct. How
the acoustic variability across speakers affects speech perception in tone languages is the overarching
question in the proposed project. Objective 1 of this project is to examine how listeners estimate relative
F0 height without cues typically considered necessary for speaker normalization. Multispeaker, level-tone
stimuli will be presented in isolation to evaluate listeners’ ability to identify relative F0 height, and
acoustic analysis will be conducted to evaluate the acoustic and perceptual basis of the identification
performance. Because the ultimate goal of speech perception is to achieve the mapping of sound onto
meaning, Objective 2 of this project is to evaluate the impact of speaker variability on accessing the form
and meaning of spoken words. The repetition and semantic/associative priming paradigm will be used to
evaluate the effect of speaker variability on spoken word recognition. With these well-established
research paradigms in speech perception, speech acoustics, and spoken word recognition, the two studies
will thematically address the issue of processing speaker variability in speech perception.
Intellectual Merit
The intellectual merit of this project is that it addresses a foundational issue in speech perception by
extending current knowledge to the suprasegmental aspect of speech. Findings from this crosslinguistic
project are expected to significantly advance current knowledge in four ways. First, suprasegmental
features are integral to speech, but they employ acoustic properties that are distinct from segmental
features. Any comprehensive theory of speech perception must account for how human listeners process
suprasegmental features in addition to segmental features. Second, acoustic properties for lexical tones
are closely associated with speaker characteristics. Investigating speaker variability in lexical tone
perception provides an opportunity to clarify the relative contribution of lexical and speaker-related F0
information to speech perception. Third, tone languages constitute the majority of the world’s known
languages. Understanding how speaker variability is processed in lexical tone perception is expected to
elucidate the universal versus language-specific aspects of speech perception. Fourth, by investigating
tone perception at both acoustic and lexical levels, the proposed project will provide a more
comprehensive view of speech perception than traditional acoustic and psycholinguistic research.
Broader Impacts
This project is expected to have broader impacts in four ways. First, it will integrate research and
education by providing extensive research training to a postdoctoral researcher, a graduate student, and an
undergraduate student aspiring to pursue a research and teaching career. It will also offer a unique
opportunity for the students to integrate the research experience into their education. Second, the
crosslinguistic nature of the project will allow contributions from speakers of other languages
traditionally underrepresented in speech and language research. Third, because part of this project will be
conducted in Hong Kong and Taiwan, the project is expected to foster international collaborations among
participating institutions. Fourth, support for this project will significantly enhance the PI’s effort in
strengthening partnerships among speech and language researchers at Ohio University and beyond.