Office noise and work performance

Field studies have shown that speech is the most distracting sound in open-plan offices. On the other hand, laboratory studies have shown that speech impairs the performance of cognitively demanding work tasks, e.g. reading and memory-recall tasks. The sound level of speech does not determine the degree of distraction caused by speech. Instead, Speech Transmission Index, STI, which correlates with speech intelligibility can explain the distracting power of speech much better. STI can be determined also between workstations in open offices. This study presents a new general model that gives the decrease in work performance as a function of STI. Work performance decreases with increasing STI. The average performance of cognitively demanding tasks decreases at least by 7 percent when speech is highly intelligible. In practical design, the ability to calculate the payback time of investments leading to proper acoustical environment is important. The new model represents the missing link in such economic estimations. This paper is based on Reference [1].