Abstract: The present invention provides for speech processing apparatus arranged for the input or output of a speech data signal and including a function generating means arranged for producing a representation of a vocal-tract potential function representative of a speech source and as an example, a speaker identification process can comprise means to capture an incoming voice signal, for example from a microphone or telephone line; means to process the signal electronically to generate a time varying series of binary vocal-tract potentials and associated non-vowel binary parameters; means to refine the signal to revoke the speaker-independent speech components; and means to compare the residual signal with a database of such residual features of known individuals.