Acoustical indicators for open-plan spaces.

Acoustical indicators currently used to qualify the satisfaction of workers towards sound in open-plan spaces are not always adapted to the situation as far as they aim at describing the acoustical properties of empty rooms (DL2, Tr, D2S). Those indicators are nevertheless recommended by national (NF S 31-080) and international standards (ISO 3382-3).
Even if the French standard in preparation (NF S 31-199) constitute an important progress on the matter of acoustical noise in open-plan spaces, in the sense that it is based on the analysis of the activity (a typology is defined) and because it recommends to use A weighted mean levels, it is still not totally appropriated. Indeed, some laboratory studies seem to show that the annoyance perceived by the people is due to the sound variation during time.
During the ANSES GABO project, several laboratory experiments have been conducted in order to evaluate the effect of different kinds of noise on performance and annoyance: phone ring, babble noise, speech more or less intelligible. Different new indicators have been tested, such as the Speech Transmission Index for non-stationary speech, inspired by Rhebergen (J. Acoust. Soc. Am., 2006) or an indicator that describes the fluctuations of the sound level. This presentation will present the comparison of these indicators in different experimental contexts.