Effects of speech intelligibility and work modality on scientific reading productivity in open-plan offices

Abstract

Speech Transmission Index (STI) is a critical indicator of speech intelligibility in quantitatively evaluating work efficiency in open-plan offices. Previous research has examined the STI-productivity relationship for simple, continuous tasks. Compared to continuous, simple tasks, interleaved complex tasks demand more effort to maintain work efficiency. However, the association of speech intelligibility with the efficiency of complex tasks remains inadequately explored. Therefore, this study investigates the impact of speech intelligibility on the productivity of interleaved scientific reading comprehension, contrasting it with productivity in continuous task modality. Thirty graduate students were recruited and exposed to irrelevant speech environments featuring speech-like pink noise as masking sound. By adjusting the sound pressure levels of speech and masking sounds, seven distinct acoustical conditions with different STI values (0.17, 0.26, 0.36, 0.45, 0.52, 0.57, and Speech_only) were created. A “Quiet” condition was also considered as a control group. Generalized Linear Mixed Models were utilized to analyze the relationships between speech intelligibility, task modality, and objective and subjective outcomes. The study found that, when the STI lies within the range of 0.26–0.45, employees must exert more effort to maintain task efficiency and resist distractions. If task-switching is involved when the STI exceeds 0.50, research efficiency further decreases. Overall, the interruption of tasks appears to amplify the impact of speech intelligibility on research efficiency. These findings underscore the importance of considering both work modality and the acoustic condition in optimizing cognitive performance and the overall user experience.