Considerations for improving the efficiency of daily calibration work of multi-channel simultaneous measurement system for sound power level determination

摘要

For sound power level determinations of information technology and telecommunications equipment (ITTE) according to the noise test codes (ISO 7779, ECMA-74, JIS X 7779 etc.), 9 or more microphone positions are required in a hemi-anechoic chamber (HAC). In HAC measurements, a multi-channel simultaneous measurement system is not only efficient for workload saving, but also indispensable for measurement accuracy (repeatability), especially for the sound sources emitting time-varying noise, such as printers, copy machines, PCs, hard disk drives etc. Though daily calibration work is one of key activities of daily measurement routines and it is also a time-consuming process due to the nature of multi-channel systems. At present, as a verification procedure, the existing noise test codes of ITTE commonly mandate such works only once during each series of measurements. But, in the near future, more stringent process will be required by a basic document, Guide 1, Guide for drafting instrumentation requirements in documents prepared by ISO/TC 43/SC 1 “Noise”. This paper discusses key issues for exact conformity of the new calibration requirements and the corresponding ideas for improving efficiency of calibration work of multi-channel simultaneous measurement system.