A view on distributed sound level sensors from the perspective of legal metrology

Paper-based calibration certificates are gradually being replaced by equivalent digital calibration certificates (DCCs). The DCC is human-readable as well as machine-readable which simplifies the administration process significantly. During calibration procedure a measurement instrument is tested on-site in a testing laboratory. However, nowadays sound level sensors are increasingly deployed as distributed systems, where they transmit measurement data from one location (e.g. a workplace in a factory) to a measurement laboratory over available networks. This data transmission process has until now not been considered during calibration procedure or type approval tests. Therefore, requirements for the data transmission process according to the regulations of the European Cooperation in Legal Metrology (WELMEC Guide) must be considered. In this project two digital sound level sensors were selected and tested when deployed as distributed systems. The data collected were used to compare the two systems in accordance with the regulations of the WELMEC guide. In this work the first example of an acoustical DCC is presented and discussed. Further, a list of requirements is proposed that should be considered in the future when developing sound level sensors intended to be used as distributed systems.