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Nasal coarticulation and sound-change: a real-time MRI study

PI: Jonathan Harrington (Munich) and Jens Frahm (Göttingen)
2017-2020
contact: Phil Hoole – hoole@phonetik.uni-muenchen.de

Project Description

Speech production is highly context-dependent because the sounds of speech overlap and influence each other in time. Typically, listeners correctly interpret speech sounds in relation to the context in which they occur, but sometimes they make errors both because speech production is inherently variable and also because there are multiple ways in perception of interpreting from an acoustic speech signal information about how the vocal organs are coordinated. The project's main objective is to understand how such variation in speech production and the ambiguous interpretation of context can accumulate into sound change. The new approach is to develop a model of various nasal-induced sound changes by analysing the temporal control of the soft palate (velum) and its perceptual consequences. Real-time magnetic resonance imaging will be used to track the movement of the velum in relation to other articulators on an unprecedentedly large scale. The focus is on nasals firstly because there are so many sound changes in the languages of the world that are driven by variation in the velum's physiological control and perceptual interpretation; and secondly because, as a consequence of the great difficulty in tracking velum dynamics accurately, we have meagre knowledge about how velum activity and associated time-course of perceived nasalisation vary across different types of contexts independently of any sound changes that are actually taking place. The project will remedy this deficiency by tracking the velum from a much larger pool of first language speakers of German (up to 30) producing a far wider range of contexts (in lax vs. tense vowels; followed by single consonants or clusters; in different prosodic contexts) than studied before. German is appropriate for such a study both because there are no known sound changes in progress involving nasals and because nasals occur in such a wide range of different contexts. This will be the first time that such a large number of subjects will participate in both physiological and perceptual experiments designed to track how the production and perceptual interpretation of nasalisation vary between speakers and listeners. This information will be used to test whether a perceptual trading relationship between the source (e.g. syllable final /n/) and contextual effect (e.g. preceding vowel nasalisation) underlies the development of phonological nasalisation. This issue will also be explored in words of different statistical frequency in order to test whether there is evidence that sound change is lexically gradual and takes hold initially in more frequently occurring words. Project spin-offs include making available the largest MRI database of nasal sound production for any language. In the longer-term, the project will lead to a deeper understanding of how the production and perception modalities are related and vary within and across speakers, and how such variation provides the conditions for sound change.