Send to:

Choose Destination
See comment in PubMed Commons below
Indoor Air. 2005 Dec;15(6):458-68.

A model predicting the effect of speech of varying intelligibility on work performance.

Author information

  • 1Laboratory of Ventilation and Acoustics, Finnish Institute of Occupational Health, Lemmink√§isenkatu, Turku, Finland.


Speech is the most distracting sound in (open-plan) offices. Several laboratory studies have shown that speech impairs the performance of, for example, reading and short-term memory. It is not the sound level of speech that determines its distracting power but its intelligibility, which can be physically determined by measuring the Speech Transmission Index (STI). The aim of this study was to develop a mathematical model that predicts how much the performance is reduced due to speech of varying intelligibility. The model was based on the literature according to which performance decrements have been 4-45% depending on the task. The best performance occurs when speech is absent (STI=0.0), and the strongest performance decrement occurs when speech is perfectly heard (STI=1.0). The shape of the performance vs. STI between 0.0 and 1.0 was adopted from the general speech intelligibility theory. The performance starts to decrease when STI exceeds 0.2. Highest performance decrease is reached already when STI exceeds 0.60.


The prediction model can be exploited in the evaluation of work performance in different acoustical conditions in open-plan offices when STI is known. It can be utilized to promote actions aiming at better acoustical conditions.

[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Blackwell Publishing
    Loading ...
    Write to the Help Desk