In this paper, we describe a novel statistical audio watermarking scheme. Under the control of the masking thresholds, watermark is embedded adaptively and transparently in the perceptual significant portions in wavelet packet domain by a statistical method. Watermark detection can be done without access to the original signal. Experimental results show the proposed scheme can survive common signal manipulations and malicious attacks. Categories and Subject Descriptors H.5.1 [Multimedia Information System]: Audio input/output, Evaluation/methodology; K.5.1 [Legal Aspects of Computing]: Hardware/Software Protection-Copyrights. General Terms Security Keywords Audio watermarking, psychoacoustic model, wavelet packet decomposition