UNIFORMITY IN PHONETIC REALIZATION: EVIDENCE FROM SIBILANT PLACE OF ARTICULATION IN AMERICAN ENGLISH

Abstract

Phonetic realization is highly variable and highly structured within and across talkers. We examine three constraints that could structure the phonetic space of related speech sounds: target, contrast, and pattern uniformity. Target uniformity requires a uniform mapping from distinctive features to their corresponding phonetic targets within a talker, contrast uniformity requires a consistent difference in the phonetic targets that realize featural contrasts across talkers, and pattern uniformity requires a uniform template of phonetic targets across talkers. Focusing on American English sibilant fricatives, we measure and compare each constraint’s influence on the phonetic targets corresponding to place of articulation. We find that target uniformity is the strongest constraint: each talker realizes a given distinctive feature value in highly similar ways across related sounds. Together with similar findings for other sound classes, this result reveals fine-grained systematicity in the mapping from phonology to phonetics and has implications for theories of speech We begin by considering a subinventory of two or more related sounds (e.g. [i] and [u], or [s] and [z]) and their corresponding phonetic targets (i.e. perceptuomotor representations). A given talker could structure the phonetic realization of these sounds by copying a pattern or template of targets that exists in the speech community and adapting it to their anatomy. This scenario allows for talker variation—one speaker’s realization of the template may be overall higher or lower on a given phonetic dimension—but otherwise it can be construed as ‘maximal phonetic structure’. Provided that the hypothetical template can be adapted to each speaker’s anatomy, this system would be fully general across the speaker population. Moreover, clear motivation for such a system exists in speech perception: if each talker has the same template of phonetic targets, perceptual adaptation would involve a simple translation of the pattern for each new talker. This is in fact assumed by many approaches to talker normalization and adaptation, especially for vowel systems (e.g. Lobanov 1971, Nearey 1978, Nearey & Assmann 2007).