Speech Intelligibility Improvement with Concrete and Abstract Auditory Cues

Objectives: The present study investigated several acoustic parameters to determine intelligibility strategies implemented by eight normal healthy individuals (NHI) and eight individuals with dysarthria (IWD) following concrete and abstract auditory speech cues. Methods: Ten acoustic parameters reportedly sensitive to intelligibility changes were selected and analyzed. Those included fundamental frequency (f₀), vowel duration, vowel-consonant-vowel syllable duration, closure duration, aspiration duration, the ratio of closure duration to closure and aspiration combined duration, the 1st & 2nd formant (F1, F2) consonant-to-vowel (C/V) ratio, and the F2 slope. They were compared in three different auditory speech cue conditions: No cue (NC), Concrete cue (CC), and Abstract cue (AC) conditions. Results: IWD showed higher values in most of the measurements compared to the NHI group. Group differences appeared in seven out of ten measurements in the NC condition. Such group differences only appeared in the closure duration and the closure duration ratio in the CC condition. Group difference disappeared in the AC condition. The results results suggested that while NHI manipulated pitch and durational aspects of speech to increase intelligibility, IWD manipulated only the durational aspect in the cue conditions. Conclusion: The pitch might already be heightened while IWD implement clear speech strategy regardless of the cue condition. The aspiration duration was unaffected by cue or group condition. Participants reduced group differences on the relational measurements (F2 C/V ratio or F2 slope) after cues suggesting that IWD maintained the ability to control relational aspects of speech because they are critical for distinctive stop production. Abstract cues appeared to make IWD’s speech closer to NHI.