[en] This report is concerned with a new method of coherence analysis for systems with feedback effect. It is shown that feedback characteristics can be analyzed using the coherence function through comparative evaluation between the coherence and the noise power contribution functions obtained by AR (autoregressive) modeling. Simulation studies using a hybrid computer as well as the analysis of JPDR-II noise data have indicated the effectiveness of the present method. It can be expected that the application of this method to investigating at-power reactor noise would yield useful information, especially on its noise source and propagation mechanism. (author)