11. The expert of OICA raised the issue of uncertainties of sound emission measurements according to UN Regulation No. 51 and some other UN Regulations (GRB-69-15). He pointed out that the uncertainties included variations within the same test laboratory (run-to-run), variations in the ambient conditions and equipment properties (day-to-day) and variations between test laboratories and road surface conditions (site-to-site). The expert from ISO reported on field experience for measuring variations according to ISO 16254 (GRB-69-26). To reduce variations and improve repeatability and reproducibility of the results, he suggested that a single microphone should be replaced with an array of microphones.

12. The experts from Germany and France proposed to address non-negligible differences in sound performance when conformity of production (CoP) tests were not carried out in the same conditions as the type approval tests (GRB-69-05). The proposal introduced conditions and procedures to be followed for test tracks comparison and for corrections to be applied on L_urban. GRB welcomed this initiative as an important starting point for further work and invited GRB experts to support it with real data.

13. GRB stressed the importance of addressing measurement uncertainties and pointed out the need to establish a new task force to this end. While OICA volunteered to provide secretariat support to the task force, GRB was not in a position to identify a governmental expert who would take the lead, due to the limited resources of competent authorities. Nevertheless, GRB was of the view that the task force should start activities as soon as possible, even without a formal leader. GRB requested the ECE secretariat to establish a dedicated website for the task force and suggested that it should meet in conjunction with the meetings of other IWGs, in order to reduce the travel expenses of participants. GRB also invited its Chair to report to the Committee for Coordination of Work (WP.29/AC.2) on the issue.