Practical consideration in application of the nearfield acoustic holography for the heavy duty diesel engine

摘要

Nearfield Acoustic Holography (NAH) system has been widely used in the automotive industryfor the noise source identification. This paper summarizes the case study to illustrate the effectsof measurement spacing, distance and scan area on noise source identification capability and tocompare the estimated sound power with the results from the sound intensity measurement.Limitation of the NAH resulted from measurement plane size, distance between the radiatingsurface and the measurement plane is shown. The topic of sound power estimation with NAHbased on the calculated sound intensity values over the area of interest is discussed. Thecalculated sound power for the particular diesel engine component with the NAH technique iscompared to the result measured with the traditional p-p type intensity probe. The importance ofproper setting of the reference microphones is reviewed using the measured data with respect tothe principal component decomposition and numbers of incoherent sources.