ABSTRACT

Purpose: This study investigated the feasibility and clinical relevance of a low-cost, wearable biofeedback system designed to monitor physiological signals related to respiration and phonation in real time. Methods: In this study, a wearable biofeedback system consisting of a thermocouple sensor and a flex sensor was designed and developed, along with a real-time feedback interface. To evaluate the system’s effectiveness, sensor data were collected from ten healthy adult participants during the performance of semi-occluded vocal tract exercises (SOVTE). The synchrony and consistency between phonation onset and abdominal motion were measured, along with the exhaled air volume and abdominal wall movement in response to variations in straw width and depth. Additionally, the effect of the water level and straw shape on the system’s performance was analyzed, with temperature changes detected by the thermocouple sensor used to predict variations in exhaled air volume. The analysis also included an evaluation of user satisfaction. Results: During phonatory tasks, the thermocouple consistently detected temperature increases ranging from 1.8°C to 5.2°C, validating its sensitivity to expiratory airflow. Larger-diameter straws (10 mm) were associated with greater temperature elevations than narrower ones (8 mm), suggesting a direct correlation with airflow resistance in water. Simultaneously, the flexible pressure sensors demonstrated stable, repeatable waveform patterns aligned with inhalation and exhalation cycles, allowing precise tracking of thoracoabdominal expansion. Real-time data visualization enabled intuitive feedback for users to self-monitor respiratory and phonatory dynamics during vocal exercises. Conclusions: These findings support the potential utility of thermocouple and flex sensors as accessible, real-time monitoring tools for individualized voice training and therapeutic intervention.