A method for measuring correlation between frequency response functions. A first frequency response function and a second frequency response function are acquired. The amplitude of the first and second frequency response functions are tabulated at a plurality of corresponding, predetermined frequencies. Amplitude and shape correlations between the first and second frequency response functions are then computed. The computed amplitude and shape correlations provide an indication of the degree of correspondence between the first and second frequency response functions, and can be used to compute a frequency response index that is an objective measure of the overall correspondence between the first and second frequency response functions.