Among the various sound sources present in open offices, intelligible speech is the one that has the greatest impact on the occupants of these spaces. Indeed, many field or laboratory studies have shown the effect of intelligible speech on annoyance or fatigue [Pierrette, 2015, Kostallari, 2017]. For several years, INRS has been working on an indicator to evaluate the emergence of speech in noise, the Meq [Chevret, 2017]. This indicator, calculated as the difference between the equivalent level of ambient noise and the level exceeded 90% of the time (Leq - L90), has already shown convincing results in the evaluation of the effect of speech during laboratory experiments [Kostallari, 2019]. However, due - in part - to the simplicity of its definition, the link between this metric and sound perception in real conditions is still too weak. In this study, a parametric analysis (measurement time resolution, frequency weighting, background noise type effect) was conducted and compares the Meq with various speech modulation indicators used to assess the acoustic quality of open offices (STI, Fluctuation strength, ...).