A semi-analytic and semiempirical formula is developed for predicting noise radiation from engine cooling fan assemblies. In this formula, the tonal sounds centered at the BPF (blade passage frequency) and its harmonics of the fan are determined by solving fluctuating forces exerted on the surrounding fluid medium by rotating blades, and the narrow and broad band sounds are described by normal distribution-like functions. The effects of shroud, upstream radiator/condenser set, and downstream engine block are approximated by shape functions. The computer model thus obtained is used to calculate the noise spectra from different fan assemblies under various working conditions and validated against the measured data. This model is used to predict the overall sound pressure levels from dimensionally similar fans running under different working conditions, and the results are compared with those estimated by the fan laws currently in use by engineers in the automotive industry.