Speech Adaptation to Kinematic Recording Sensors: Perceptual and Acoustic Findings.

Abstract

This study used perceptual and acoustic measures to examine the time course of speech adaptation after the attachment of electromagnetic sensor coils to the tongue, lips, and jaw. Twenty native English speakers read aloud stimulus sentences before the attachment of the sensors, immediately after attachment, and again 5, 10, 15, and 20 min later. They read aloud continuously between recordings to encourage adaptation. Sentence recordings were perceptually evaluated by 20 native English listeners, who rated 150 stimuli (which included 31 samples that were repeated to assess rater reliability) using a visual analog scale with the end points labeled as "precise" and "imprecise." Acoustic analysis began by segmenting and measuring the duration of the fricatives /s/ and /ʃ/ as well as the whole sentence. The spectral center of gravity and spectral standard deviation of the 2 fricatives were measured using Praat. These phonetic targets were selected because the standard placement of sensor coils on the lingual surface was anticipated to interfere with normal fricative production, causing them to become distorted. Perceptual ratings revealed a decrease in speech precision after sensor attachment and evidence of adaptation over time; there was little perceptual change beyond the 10-min recording. The spectral center of gravity for /s/ decreased, and the spectral standard deviation for /ʃ/ increased after sensor attachment, but the acoustic measures showed no evidence of adaptation over time. The findings suggest that 10 min may be sufficient time to allow speakers to adapt before experimental data collection with Northern Digital Instruments Wave electromagnetic sensors.