A speech signal is sampled to form a sequence of speech data and segmented into segments. The envelope of each segment is detected to form an envelope segment. Each datum of the segment is divided by each datum of the envelope segment to form a de-envelope segment which is transformed into spectral components. Dominant frequencies are determined for the spectral components with greatest magnitudes. Envelope coefficients are generated by fitting a polynomial function to the segment. Phase parameters are generated representing a phase of each of the dominant spectral components. The dominant frequencies, the envelope coefficients and the phase parameters are generated as compressed speech data for each voiced segment. For each unvoiced segment, a carrier frequency, an amplitude and at least one sideband frequency of an amplitude modulation component are generated as the compressed speech data.