4. A wideband speech signal reconstruction method comprising: a first step wherein an input narrowband speech signal is spectrum-analyzed; a second step wherein the spectrum-analyzed results obtained in said first step are vector-quantized using a narrowband speech signal codebook; and a third step wherein the quantized values obtained by said vector quantization in said second step are reconstructed to obtain a wideband speech signal through use of a representative waveform codebook.
4. A wideband speech signal reconstruction method comprising: a first step wherein an input narrowband speech signal is spectrum-analyzed; a second step wherein the spectrum-analyzed results obtained in said first step are vector-quantized using a narrowband speech signal codebook; and a third step wherein the quantized values obtained by said vector quantization in said second step are reconstructed to obtain a wideband speech signal through use of a representative waveform codebook. 8. The method of claim 4, 5, or 7 wherein, in the reconstruction of said quantized values to a speech signal through use of said representative waveform codebook, waveform segments of said representative waveform codebook corresponding to said quantized values are overlapped pitch-synchronously for voiced speech and waveforms of a length corresponding to an analysis window shift width are randomly selected for unvoiced speech.