SOUND POWER ASSESSMENT, NOISE SOURCE IDENTIFICATION & DIRECTIVITY ANALYSIS OF COMPACTION MACHINES

NVH has gained importance in the field of earth moving equipment due to the demand of quieter machines and stringent in-cab as well as exterior noise emission norms. Several parts of the world have adopted strict legislation on noise emission by earth moving equipment, but many countries have not adopted any regulations till date. This paper mainly focusses on helping governing bodies as well as machine manufacturers in adopting simple yet accurate testing method for compaction machine. The study consists of directivity analysis, noise source identification & noise source ranking and 4-point microphone position sound power evaluation method applied to compactors with wide range of engine power ratings. All the tests in 4-point method and directivity analysis were performed under stationary as well as dynamic conditions. Currently, several countries and vehicle manufacturers have adopted sound power evaluation of compactor exterior noise emission by 6-point method (as per ISO6393 & ISO6395) which consists of six microphone positions. The 4-point method presented in this paper tries to reduce measurement positions from 6 to 4, thereby simplifying the testing method, reduce instrumentation cost and measurement time. Error between the two methods was found out to be less than 1%. Directivity analysis shows that the compactor is extremely directive at its rear side & emitted maximum sound power. Whereas it is observed that microphone positions mentioned in ISO standards are not suitable enough to capture this noise which results in underestimation of exterior sound power level.