3. The method of claim 1 wherein the profile constructing step includes the steps of detecting the frequency distribution of the energy of the utterance for a plurality of time intervals within the duration of a single phoneme, and deriving at least a pair of sweep spectra representing the change in energy present in the phoneme from one frequency to another as a function of time for a plurality of frequency distributions, and wherein the difference profile generating step includes generating a pair of difference profiles for substantially each pair of significant phonemes by subtracting the respective sweep spectra of each significant phoneme from the respective sweep spectrum of each other significant phoneme.
3. The method of claim 1 wherein the profile constructing step includes the steps of detecting the frequency distribution of the energy of the utterance for a plurality of time intervals within the duration of a single phoneme, and deriving at least a pair of sweep spectra representing the change in energy present in the phoneme from one frequency to another as a function of time for a plurality of frequency distributions, and wherein the difference profile generating step includes generating a pair of difference profiles for substantially each pair of significant phonemes by subtracting the respective sweep spectra of each significant phoneme from the respective sweep spectrum of each other significant phoneme. 5. The method of claim 3 wherein the sweep spectra deriving step includes deriving a short time constant sweep spectrum having a first time constant, and deriving a long time constant sweep spectrum having a time constant longer than the first time constant.