Natl. Inst. of Standards and Technol., Sound Bldg. 233, Rm. A147, Gaithersburg, MD 20899-0001
In every advanced industrial nation, urgent needs for accurate, impartial measurement capabilities without unnecessary duplication of laboratories have led to the establishment of a national primary metrology and standards laboratory. These laboratories conduct international comparisons of calibrations and measurements intended to demonstrate sufficiently close agreement, or to reveal and to resolve unexpected discrepancies, among results from different nations. Such comparisons must precede, accompany, and continually sustain agreements regarding legal metrology and product conformity assessment, which are essential to the fair and successful conduct of international trade. These laboratories also provide scientific and technical support to the development of international standards, as well as the domestic standards of their respective individual nations. A national laboratory typically meets the critical needs of that nation's private and public calibration laboratories for state-of-the-art measurement services through an instrument calibration hierarchy comprising direct or implied chains of ``traceability'' to the national laboratory. Selected, consequential international comparisons of electroacoustical calibrations from national laboratories are discussed. Examples of research in acoustical metrology at NIST and the measurement services provided to its customers are described.