Locus equations during compensatory articulation: A test of the ‘‘orderly output constraint.’’

Abstract

Previous research [Sussman etal., J. Acoust. Soc. Am. 90, 1309–1325 (1991); 94, 1256–1268 (1993)] showed that frequency of F2 onsets (for syllable-initial voiced stops /bdg/) is a linear function of F2 as measured in the vowel nucleus and the particular linear function relating these parameters is itself a function of stop place of articulation. This linear relationship has been demonstrated cross-linguistically as well as across consonantal manner classes (fricatives, nasals, approximates). The purpose of this study was to determine how altered articulatory kinematics (via bite blocks) affects the linearity and place coding of locus equations. Six speakers produced CV/t/ tokens with initial /bdg/ followed by ten medial vowels. F2 onset (Hz) and F2 midvowel (Hz) were measured via spectrographic, LPC, and FFT spectra. Despite bite blocks locus equations were remarkably linear, and slopes/y intercepts consistently contrasted stop place. A functional role for the acoustic linearity of CV transitions in the output signal, despite gross alterations in articulatory gestures, is offered based on auditory perceptual requirements necessitated by the neural encoding of F2 transitions. These ideas are described within a new theoretical framework—the ‘‘orderly output constraint.’’