Measurement uncertainty of ISO CD 23351-2: acoustic performance of furniture ensembles and enclosures in situ

Enclosures (E), such as mobile pods or rooms, and partial enclosures (PE), such as sofa groups and open pods, are increasingly used in indoor environments where occupants temporarily need better speech privacy or peace of work. Such objects are usually tested in laboratory using ISO 23351-1. That standard excludes very large objects. In addition, acousticians need to measure objects in situ. The field method, ISO CD 23351-2 is based on sound power level tests according to ISO 3744 standard. The main outcome is apparent speech level difference, D’S,A [dB]. Since the method of ISO CD 23351-2 is novel, information about measurement uncertainty (MU) is lacking. Our purpose was to determine the uncertainty by conducting two independent studies: 1. between-laboratory study and 2. between-room study. In study 1, thirteen participants tested one PE and one E in the same room. Based on eight accepted participants, the between-laboratory standard deviations (SD) of D’S,A were 0.8 dB for PE and 0.7 dB for E. In study 2, a single participant tested one PE and one E in ten different rooms. The between-room SDs of D’S,A were 0.6 dB both for PE and E. The total SD was 1.0 dB and it considers the MUs both due to operator and room choice. The results can be useful in the finishing of ISO 23351-2 standard. Our study also provides data regarding the MU of ISO 3744 and ISO 3382-2 standards.