The international standard, ISO/IEC 17025 was developed to determine technical competence
and to evaluate laboratories throughout the world. Accreditation bodies playing a vital
role are increasingly using proficiency testing methodology as a tool to ensure the
credibility of their accreditation programs. The successful completion of a well-designed
proficiency test can validate the measurement method and uncertainty budgets of a testing
laboratory. Additionally, proficiency tests can provide a good indication about the
quality of the test results. An important part of inter-laboratory comparisons and
proficiency testing is the determination of the associated error analyses which are
focused on uncertainty values. This paper presents the implementation of proficiency tests
using inter-laboratory methodology among five different acoustic laboratories. These tests
were carried out on 5.27 KWCooling standard unitary air conditioner, A/C, such
as through-wall or split room standard A/C units, for the assessment of Housing &
Building National Centre acoustic laboratory. Analyses of results show a good agreement
for En-Value among the selected laboratories
when compared with the lowest uncertainty as stated by proficiency tests standards.