An audio watermarking algorithm based on EMD(Empirical Mode Decomposition) was proposed.Residual signal components decomposed from EMD were selected to embed watermark by the proposed algorithm and the watermarked components are proved to be still residual signal components

which provides the theoretical basis for the watermark embedding and extraction.The optimal audio watermark embedding strength in EMD was solved by particle swarm optimization algorithm.The robustness and imperceptibility of watermarking can be satisfied according to this embedding strength.The simulation results show that using the optimal embedding strength to embed watermark can guarantee the imperceptibility and robustness of the watermark in most attack conditions.