In a CELP type speech coder, the excitation is quantized by vectors from a random codebook. The random codebook is made of a fixed waveform storage section (181), followed by a vector rearranging unit (182). The rearranging section (182) shifts the vectors to positions determined to minimize the quantization distorsion using a pulse placement methodology of an algebraic coder. The vectors are summed (183) to generate the excitation code vector.