Noise source identification in turbomachinery often requires estimation of the correlation between multiple rotating (aerodynamic) sources and the stationary radiated sound field. When treated as a multiple input/output problem, relative motion between input (sources) and output signals has the effect of amplitude and phase, modulating the input. The resulting nonlinearities introduced into the system affect the estimation of the coherence function. A straightforward approach will be used to examine the AM and PM effects as they pertain to the multiple input/output model for rotating sources. As pointed out in the literature on rotating diffuser models [Elko, M.S. thesis, Pennsylvania State University (1980)], source directivity plays a significant role in determining the strength of the AM spectra. This point is best illustrated by comparing the results of rotating monopoles and dipoles, and extrapolating these results to other radiation patterns. The consequences of PM are viewed through the general Doppler formula, applied to the specific geometry of rotating sources in an arbitrary plane with respect to a fixed observer. The possibility of removing the AM/PM effects by prepossessing the signals will also be discussed.