Associations between tongue movement pattern consistency and formant movement pattern consistency in response to speech behavioral modifications

Abstract

The degree of speech movement pattern consistency can provide information about speech motor control. Although tongue motor control is particularly important because of the tongue's primary contribution to the speech acoustic signal, capturing tongue movements during speech remains difficult and costly. This study sought to determine if formant movements could be used to estimate tongue movement pattern consistency indirectly. Two age groups (seven young adults and seven older adults) and six speech conditions (typical, slow, loud, clear, fast, bite block speech) were selected to elicit an age- and task-dependent performance range in tongue movement pattern consistency. Kinematic and acoustic spatiotemporal indexes (STI) were calculated based on sentence-length tongue movement and formant movement signals, respectively. Kinematic and acoustic STI values showed strong associations across talkers and moderate to strong associations for each talker across speech tasks; although, in cases where task-related tongue motor performance changes were relatively small, the acoustic STI values were poorly associated with kinematic STI values. These findings suggest that, depending on the sensitivity needs, formant movement pattern consistency could be used in lieu of direct kinematic analysis to indirectly examine speech motor control.

FIG. 1.

(Color online) Time history of posterior tongue movement in medial-lateral (X), anterior-posterior (Y), and ventral-dorsal (Z) dimensions and the resulting principal component signal (PC).

FIG. 2.

First and second formant movements during the target utterance before interpolation (top) and after interpolation (bottom).

FIG. 3.

Time history of the interpolated first and second formant movements (F1 inverted) and the corresponding principal component signal.

FIG. 4.

Association of kinematic and acoustic STI measures based on performance of younger and older adults during typical speech (top) and during various speech behavioral modifications (bottom).

FIG. 5.

Means (±SE) of the kinematic STI (top) and the acoustic STI (bottom) across speech tasks.

FIG. 6.

Means (+SE) of utterance durations (top) and vocal intensities (bottom) of younger and older adults across all speech tasks.