Bat inspired optimization approach for audio watermarking algorithm

Digital audio watermarking still remains one of the most interesting techniques for multimedia copyright protection. In this paper, bat inspired optimization approach is exploited to design an optimal audio watermarking algorithm for copyright protection. First, the original audio signal is decomposed by the Discrete Wavelet Transform (DWT) into low and high frequency parts. The low frequency part is then segmented into several 2-D blocks, and QR factorization is subsequently applied to each one. The watermark, which is a binary logo, is embedded by quantizing the coefficients of resulting R matrices. Since the quantization step is signal-dependent, bat algorithm optimization is used to find a suitable one for each audio signal. This allows to obtain the highest possible robustness without losing the transparency of the watermark. Simulation tests show that the proposed method not only maintains high quality of the audio signal, but also is robust against common signal processing manipulations such as noise addition, re-sampling, filtering and MPEG 1 Layer III compression.