  The ISO 3382-3 standard (2012) defines single number quantities (SNQs) which
evaluate the acoustic quality of open-plan offices, but does not address the
issue of measurement uncertainties. This study focusses on the SNQs present in
this standard related to spatial decay of speech, i.e. D 2S , L pAS4m and r c.
The aim is to provide additional information to the limited literature on the
measurement uncertainties of these SNQs by use of both analytical developments
and a stochastic approach based on simulations. The accuracy of the analytical
developments was studied thanks to simulations of the sound propagation within
a series of offices (1 layout, 16 acoustic configurations with different screen
heights and different acoustic qualities of screens and ceiling). The SNQs
obtained in the simulations cover a wide range: D 2S between 3.4 and 7.5 dB(A),
L pAS4m between 40.6 and 51.9 dB(A) and r c between 2.5 and 14.7 m. Therefore,
the simulations are representative of a broad set of acoustic qualities.
Estimated uncertainties have a magnitude of 0.4 dB(A) for D 2S and vary between
0.4 and 0.7 dB(A) for L pAS4m and between 0.2 and 1.5 m for r c over a
measurement path comprising 7 measurement positions. The simulations also raise
the question of describing the acoustic quality of an office using a single
value for the indicators. The results of the simulations show that in some
cases, D 2S values significantly depend on the measurement path, leading to a
strong increase of its measurement uncertainty if a unique value is to be
considered.
