Partial coherence function is formulated for multiple noise/energy source problems associated with linear systems, and the pitfalls in the use of noise/energy source identification in linear systems are investigated. The analytical results show that the partial coherence function in two input/single output linear systems is susceptible to not the signals but the extraneous noises unless the inputs are completely independent and the signal/noise ratios are high. Simulations and experiments are also carried out to demonstrate the fact that partial coherence function is not suitable for noise/energy source identification in linear systems.
