Irrelevant speech sound level effects on sustained attention in an open-plan office

Vollständiger Abstract

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Open-plan offices are valued for flexibility and space efficiency, yet irrelevant speech remains a primary source of acoustic dissatisfaction. This study examined how irrelevant-speech sound pressure level (SPL) affects sustained attention and physiological load in a simulated open-plan office. Twentyfour participants performed the Sustained Attention to Response Task (SART) under four conditions: a background-only control (LAeq 35–40 dB(A)) and irrelevant speech at 40–45, 45–50, and 50–55 dB(A). Behavioural outcomes were analysed alongside electrodermal activity (EDA, n = 24) and prefrontal EEG measures (valid n = 16). Linear mixed-effects models revealed no significant effect of SPL on mean behavioural performance. However, sympathetic arousal differed across conditions: relative change in skin conductance level (∆SCL) was higher at 50–55 dB(A) than at 40–45 dB(A) (p = 0.014, Cohen’s dz = 0.54). In the EEG subset, mean task engagement did not differ between SPLs, but increased over time only at 50–55 dB(A) (p = 0.002). These results indicate that elevated speech levels impose measurable physiological costs even when short-term behavioural performance is maintained, supporting the integration of physiological indicators into post-occupancy evaluation and the prioritisation of design measures to limit speech levels in open-plan workplaces.