Variation in /u/ fronting in the American Midwest

Objective speech outcomes after surgical treatment for oral cancer: An acoustic analysis of a spontaneous speech corpus containing 32.850 tokens

INTRODUCTION

Surgical treatment for oral cancer leads to lasting changes of the vocal tract and individuals treated for oral cancer (ITOC) often experience speech problems. The purpose of this study was to analyse the acoustic properties of the spontaneous speech of individuals who were surgically treated for oral cancer. It was investigated (1) how key spectral measures of articulation change post-treatment; (2) whether changes are more related to target manner or place of articulation; and (3) how spectral measures develop at various time points following treatment.

METHOD

A corpus consisting of 32.850 tokens was constructed by manually segmenting the speech of five (four female - one male) American English speaking ITOC. General acoustic characteristics (duration and spectral tilt), plosives (burst frequency), fricatives (centre of gravity and spectral skewness), and vowels (F1 and F2) were analysed using linear mixed effects regression and compared to control speech. Moreover, a within speaker analysis was performed for speakers with multiple recordings.

RESULTS

Manner of articulation is more predictive of post-treatment changes than place of articulation. Compared to controls, ITOC produced the fricatives /f, v, θ, ð, s, z, ʃ, ʒ/ with a lower centre of gravity while no differences were found for plosives and vowels. Longitudinal analyses show high within-speaker variation, but general improvements one-year post-treatment.

CONCLUSIONS

Surgical oral cancer treatment changes the spectral properties of speech. Fricatives with varying manner of articulations were distorted, suggesting that manner of articulation is more predictive than place of articulation in identifying general problem areas for ITOC.

Increased speech contrast induced by sensorimotor adaptation to a nonuniform auditory perturbation

When auditory feedback is perturbed in a consistent way, speakers learn to adjust their speech to compensate, a process known as sensorimotor adaptation. Although this paradigm has been highly informative for our understanding of the role of sensory feedback in speech motor control, its ability to induce behaviorally relevant changes in speech that affect communication effectiveness remains unclear. Because reduced vowel contrast contributes to intelligibility deficits in many neurogenic speech disorders, we examine human speakers' ability to adapt to a nonuniform perturbation field that was designed to affect vowel distinctiveness, applying a shift that depended on the vowel being produced. Twenty-five participants were exposed to this "vowel centralization" feedback perturbation in which the first two formant frequencies were shifted toward the center of each participant's vowel space, making vowels less distinct from one another. Speakers adapted to this nonuniform shift, learning to produce corner vowels with increased vowel space area and vowel contrast to partially overcome the perceived centralization. The increase in vowel contrast occurred without a concomitant increase in duration and persisted after the feedback shift was removed, including after a 10-min silent period. These findings establish the validity of a sensorimotor adaptation paradigm to increase vowel contrast, showing that complex, nonuniform alterations to sensory feedback can successfully drive changes relevant to intelligible communication.NEW & NOTEWORTHY To date, the speech motor learning evoked in sensorimotor adaptation studies has had little ecological consequences for communication. By inducing complex, nonuniform acoustic errors, we show that adaptation can be leveraged to cause an increase in speech sound contrast, a change that has the capacity to improve intelligibility. This study is relevant for models of sensorimotor integration across motor domains, showing that complex alterations to sensory feedback can successfully drive changes relevant to ecological behavior.