At present, the absolute comparison test (ISO 3744:1994(E)) is the most used engineering method to correct the acoustic environment in internal combustion engines industry. Starting from the basics of the absolute comparison test, this paper presents a improved engineering method. As the measurement uncertainty theory abandons the classification of the systematic and random error in the traditional theory and scientifically reflects the reliability of measurement data, this paper deals with the measurement uncertainty theory into more depth. On the basis of a concrete example, formulas for environmental correction and uncertainty measurement were derived. The uncertainty results were compared with those obtained using the absolute comparison test. The two-surface method uncertainty coefficient was deduced and also verified by an engineering example. It is believed that the use of methods including uncertainty theory and uncertainty measurement provide a more solid basis for improved noise reduction. Hence, this provides a benefit in terms of international market competition within the internal combustion engine industry.
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