Publication Details
Abstract
Effective public speaking depends not only on the quality of verbal content but also on the speaker’s vocal delivery. Among the various dimensions of vocal performance, voice modulation plays a particularly important role in shaping audience attention, emotional engagement, and speaker credibility. The present study investigated how variations in pitch, tone, pacing, volume, and vocal emphasis influence audience perceptions of public speaking effectiveness. Using a controlled experimental design, 120 undergraduate students viewed one of four video-recorded speeches manipulating vocal modulation (high vs. low) and content quality (strong vs. weak). Audience evaluations were measured across four dimensions: credibility, engagement, clarity, and overall competence. Results demonstrated that speakers employing dynamic and varied voice modulation received significantly higher ratings across all categories regardless of content quality. The highest evaluations were assigned to speakers combining strong content with expressive vocal delivery, while monotone speakers received comparatively lower ratings even when presenting well-structured speeches. The findings confirm that voice modulation functions as a powerful communicative tool capable of substantially shaping audience perception and public speaking effectiveness. The study carries important implications for communication pedagogy and EFL speaking instruction.