In this paper, we will propose a robust watermarking system for digital audio sound to protect the copyright of publication and claim of ownership. The proposed watermarking scheme uses the frequency extent between 1 Hz and 20 Hz, which cannot be heard by the unaided human ear, to embed the watermark. Thus, the original audio quality will not be influenced by the watermark. Currently, the techniques of Perceptual Audio Coder contain MPEG-1, -2, -2.5, MPEG-2 AAC, MPEG-4 AAC and Window Media Audio. From experimental results, the proposed watermarking system can resist attacks of previous audio coders and low bit-rate compression. The watermark is extracted with 100% correction after previous encoder attacks. Furthermore, to authenticate the audio signal, the system can quickly extract the watermark without the knowledge of original audio signals.