Background: In open-plan office rooms, one of the main reasons for the nuisance of work is the noise from employees’ conversations. In order to limit it, the permissible values of the parameters characterizing the acoustic properties in those rooms on a 2-level scale are defined. Material and Methods: The article introduces a 3-level scale for assessing the acoustic properties (bad, fair, good) of a room based on EN ISO 3382‑3:2012 and PN-B-02151-4:2015 – criterion 1. Additionally and alternatively, a new 3-level scale assessment criterion (criterion 2), concerning acoustic separation between groups of workstations, was determined. In order to meet that criterion, it is necessary to take into account the acoustic treatment of the room. A multivariate (7) acoustic treatment studies were performed using computational simulation methods. Results: Requirements, according to PN-B-02151-4:2015, were met after the application of a sound-absorbing suspended ceiling and acoustic screens at workplaces. To meet the requirements of EN ISO 3382‑3:2012, it was necessary to additionally use sound-absorbing materials on the walls and acoustic screens separating the naves of the room. To meet the requirements of criterion 2, it was necessary to additionally use acoustic screens separating groups of workstations and acoustic screens in passages. Conclusions: Appropriate acoustic properties can be obtained in open space offices. Appropriate acoustic properties can be obtained in open-space offices. The requirements according to PN-B-02151-4:2015 can be met with much lower acoustic treatment than the requirements according to EN ISO 3382‑3:2012. The use of a 3-level scale for assessing the acoustic properties of a room allows for the differentiation of rooms with regard to their acoustic properties. The introduction of a new assessment method, taking into account the grouping of workplaces in a room, makes it possible to assess the acoustic properties of a room in a more reliable way, by neglecting the impact on the assessment of areas where people are not present. Med Pr. 2021;72(4):375–90