In this thesis, we propose an audio watermarking system based on wavelet packet decomposition and psycho-acoustic modeling. The audio watermarking system can deliver perceptual transparent audio quality, and it is robust against various signal processing or malicious attacks.

The original audio signal is first segmented and divided into 29 subbands via wavelet packet decomposition. The bandwidth allocation of the subband decomposition structure is close to the critical band structure of human auditory system. Middle and middle-low subbands are chosen for watermark embedding. A selective embedding method is used to embed watermark into those coefficient blocks with clear block polarities. Modification of selected coefficients is based on the minimum masking threshold of psycho-acoustic model. Instead of the original Audio signal, a secure key is used in the watermark extraction to indicate the locations where watermark bits are embedded. In addition, a synchronization mechanism is imposed to search for the frame boundary of attacked audio signal.

Simulation results show that the watermarking system is robust against MP3 compression at 48 Kbps and above. It also survives StirMark attacks for audio and cropping attacks.