Methods of Passby Noise Prediction in a Semi-Anechoic Chamber 971989

This paper addresses the indoor passby noise measurement techniques satisfying SAE J1470 Recommended Practice. The restrictions of the suggested methods are also investigated. We suggested the passby noise measurement method in a large semi-anechoic chamber. We also have tried two prediction methods using array microphone system to predict the passby noise in a small-size semi-anechoic chamber. The first method is based on the line array microphone method. This method is found to be only applicable in the nearfield, because spherical Hankel function is used as a basis function. This is just simple consequence of fact that the basis functions are not separable in the farfield. The second one is the well-known nearfield acoustic holography(NAH). Not only the detailed procedures of applying NAH to the passby noise prediction but also the drawback of this method are discussed.