Acoustic design of open-plan offices (NT TR 619)

Abstract

The acoustic conditions in open-plan offices were investigated in a Nordic cooperation project. Measurements were carried out in five open-plan offices along with a questionnaire to gather the staff’s subjective judgments. A programme for the acoustic measurements was drawn up, specifying how to perform the measurements and which type of parameters to measure. The acoustic parameters included are Reverberation time T20, Early decay time (EDT), Clarity (C50), Speech transmission index (STI), Speech intelligibility index (SII), Privacy index (PI), Rate of spatial decay of sound pressure levels per distance doubling (DL2 ), Excess of sound pressure level with respect to a reference curve (DLf), and background noise levels in occupied and unoccupied offices. A refurbishment programme was carried out in two of the offices. Measurements were performed after refurbishment and a questionnaire was completed. It is concluded that parameters relating to sound propagation, such as DL2 and DLf, are appropriate for the acoustic evaluation of open-plan spaces. A refurbishment programme was carried out in two open-plan offices. It has been shown that DL2 and DLf are sensitive to the acoustic treatment carried out and that they also reflect an improvement in the subjective judgment as regards the acoustic environment in general. Moreover, these parameters can be converted into a (comfort) radius indicating the distance for achievement of a certain reduction of the sound level from a sound source. This application could serve as a practical tool for the acoustic planning of open-plan offices.