1. A method for processing a speech signal comprising steps of: identifying a plurality of portions of said speech signal representing individual speech pitches; generating an encoded speech signal from a plurality of said speech pitches, said encoded speech signal retaining ones of said plurality of pitches and omitting other ones of said plurality of pitches, at least one speech pitch being omitted for each speech pitch retained; and generating a reconstructed speech signal by replacing each said omitted pitch with an interpolated replacement pitch having signal waveform characteristics which are interpolated from a first retained reference pitch occurring temporally earlier to said pitch to be interpolated and from a second retained reference pitch occurring temporally later than said pitch to be interpolated.
2. The method in claim 1, wherein said step of generating a reconstructed speech signal comprises the steps of: interpolating said replacement pitches to have signal values that are linear interpolations of the signal amplitude values of the temporally earlier and temporally later pitches at corresponding times relative to the start of the pitches.