Simplified expressions of uncertainty for single number quantities in ISO 3382-3 (2022)

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The ISO 3382-3 (2022) standard defines single number quantities (SNQ) characterizing the spatial decay of speech (D2S, LpAS4m, rc) and of its intelligibility (rD). Relying on a Round-Robin test performed in a single office, the standard evaluate the precision of measurement using a unique value of uncertainty for each SNQ. To make this assessment more accurate, analytical expressions have been established by applying the law of propagation of uncertainty. These expressions, although precise, are too complex to be included in the standard. This work consists in simplifying them, relying on 95 measurements realized in 36 companies in France and Germany. Firstly, the terms associated with distance measurement uncertainties were found to be negligible. Secondly, the estimation of the uncertainties of A weighted speech levels and Speech Transmission Index, based on the measurements made at the workstations constituting the 95 paths, enabled further simplifications. Finally, simplified expressions turn out to be as accurate as the original expressions, and the estimated uncertainties are comparable to those reported by Yadav et al. (2019).