Interlaboratory comparison of ISO 23351-1: speech level reduction of furniture ensembles

International standard ISO 23351-1:2020 describes a laboratory method for declaring the speech level reduction DS,A of furniture ensembles (such as partially enclosed pods or workstations) and enclosures (such as phone booths). Such products are increasingly used in lounges, hospitals, education buildings, open-plan offices, and similar places to provide local places of improved speech privacy or concentration. DS,A describes how much the product reduces the A-weighted sound power level of standard speech to the exterior space. The method is based on repeated application of ISO 3741 standard. The purpose of our study was to determine the precision of the ISO 23351-1 method for two extreme kinds of products that the method covers: a workstation and a phone booth. Eight independent laboratories from six countries participated in the accuracy experiment. Two specimens were circulated in these laboratories and tested according to ISO 23351-1. Measured DS,A values varied from 3.7 to 5.5 for the workstation and from 27.2 to 30.3 dB for the booth. The corresponding reproducibility standard deviations were 0.6 and 1.1 dB, respectively. The results have been exploited in the ISO 23351-1 standard.