Project Summary: Processing Speaker Variability in Lexical Tone Perception
1
Project Summary
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, research on suprasegmental features (e.g., lexical tones) in non-English languages
is relatively scarce. The proposed project investigates how speaker variability affects the processing of
lexical tones in speech perception. 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. Objective 1 of this project is to examine
how listeners estimate relative F0 height without cues typically considered necessary for speaker
normalization. Because pitch perception is also integral to music perception, the role of musical
background in F0 height estimation will also be explored. Objective 2 is to examine the effect of speaker
variability, relative to other sources of acoustic variability, on native and nonnative perception of lexical
tones. Objective 3 is to evaluate the impact of speaker variability on accessing the form and meaning of
spoken words in tone and nontone languages. To these ends, three integrated studies will be conducted
with established research paradigms in speech perception (tone identification), speech acoustics (acoustic
analysis), and spoken word recognition (repetition and semantic/associative priming).
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 three primary ways. First,
suprasegmental features are integral to speech. They employ a set of acoustic properties that are distinct
from those for segmental features. Any comprehensive theory of speech perception must account for how
human listeners process speaker variability in suprasegmental 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 speakerrelated pitch 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.
This project is expected to make broader impacts in four ways. First, it will integrate research and
education by providing extensive research training to graduate students aiming to pursue a research and
teaching career. It will also offer a unique opportunity for undergraduate students in related disciplines to
integrate research experiences 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. Because part of this project will be conducted in Taiwan, it is expected to foster
international collaborations between participating institutions. Third, support for this project will
significantly enhance the PI’s effort in strengthening partnerships among speech and language researchers
at and beyond Ohio University. Finally, the potential benefits to society can be illustrated by two
examples. Understanding similarities and difference between native and nonnative tone perception will
contribute to improving and strengthening instruction of lexical tones, one of the most challenging aspects
of learning a tone language. Knowledge of the relationship between musical pitch perception and lexical
tone perception is expected to inspire further research on the intriguing connection between music and
language, two of the most significant human activities.