Implications of Speech Exposure for Working Memory and Perceived Workload

Licentiate thesis, 2026

Background speech is common in many modern work environments, particularly in open-plan offices, where it has been associated with increased disturbance and impaired cognitive performance. Although the effects of irrelevant speech on cognition have been demonstrated previously, the acoustic factors and cognitive processes contributing to these effects are still not fully understood.

This thesis investigates how background speech influences working memory performance and perceived workload under controlled acoustic conditions. A series of listening experiments was conducted in which participants performed cognitive tasks while being exposed to different speech conditions. The experiments examined the effects of varying reverberation time, semantic content, and sound level.

The results show that exposure to background speech negatively affects working memory performance and increases perceived workload compared to silence, and demonstrate that the disruptive effect of speech depends on characteristics of the signal itself. Higher speech levels were associated with stronger disruption, while speech-like temporal structure appeared to contribute more strongly to the effect than semantic content alone. Furthermore, perceived workload increased even when objective performance remained relatively stable, suggesting that maintaining performance under speech exposure may require additional mental effort.

The findings contribute to a broader understanding of how different characteristics of speech influence both cognitive performance and subjective experience. The work highlights the importance of considering both objective and subjective measures when evaluating the impact of speech exposure and suggest that reducing the prominence of background speech may be important for supporting cognitive functioning and limiting mental strain during sustained work tasks.