BACKGROUND. Colleagues' speech is a common disturbance in offices, especially in open-plan offices. Irrelevant speech influences cognitive performance and subjective ratings of acoustic satisfaction as well as environmental satisfaction. However, only few studies have examined simultaneously physiological, performance, and psychological consequences background speech has on humans. 

AIM. The purpose was to compare psychological experiences, cognitive performance, and physiological responses in two sound conditions: speech and silence. 

METHODS. We tested 21 subjects in the speech group and 19 subjects in the silence group (sound level of ventilation 35 dB LAeq). Speech was played at sound level 65 dB LAeq, which people were supposed to ignore while making cognitive tasks and answering questionnaires. The sound condition lasted on average for 48 minutes. Participants' performance, psychological experience and various physiological stress reactions (e.g. stress hormone levels, heart rate variability) were measured. 

RESULTS. The speech group had lower performance and higher physiological stress level than the silence group. Speech was subjectively estimated more annoying and loading, but less tiring than silence. 

PRACTICAL IMPLICATIONS. This study shows that speech influences experience, performance, and physiological stress level. Therefore, its influence should be minimized in offices, where work requiring concentration is needed.