Cepstral Coefficients are a set of coefficients that represent the cepstrum of a signal. Cepstrum is the result of taking the fournier transform of a signal's db spectrum. In audio, frequently cepstral coefficients are used with the Mel-Scale, which is then refered to as Mel-Frequency Cepstral Coefficients (MFCC), though there is some debate as to the usefulness and necessity of Mel scaling in this context(for example, here).

-- BenFields - 05 Mar 2007