A Preliminary Study Investigating How Voice Pitch and Speech Style Influence Driver Performance and Emotion Reflections in In-Vehicle Assistance Systems

As the adoption of autonomous vehicles continues to grow, understanding the impact of auditory features in driving assistance systems becomes increasingly crucial. This study investigates the effectiveness of different voice pitches (alto and bass) and speech styles (frozen and casual) in enhancing driver recognition and compliance with in-vehicle reminders. A total of 12 participants engaged in two experimental sessions, providing a dataset of 46,095 emotion data points. Meanwhile, the research observation method was utilised to collect participants’ performance data. An online survey with 5-Likert scale followed the experimental sessions to collect data regarding users’ satisfaction. The findings reveal that alto voice pitch significantly improved compliance for safety-critical reminders (seatbelt check: 92% vs. 58%, p = 0.046), and frozen speech style significantly improved compliance during high-intensity driving (obstacle reminder: 58% vs. 25%, p = 0.046). Notably, while these effective auditory features evoked higher negative emotions (e.g., alto evoked sadness with a mean value of 0.222 vs. 0.162 for bass during pre-driving), participant satisfaction remained high (alto: M = 4.17/5; frozen: M = 4.00/5). These results suggest implications for designing customizable voice features in in-vehicle assistant systems to enhance driver experience and safety.