In this book chapter, we present an overview of our time-frequency (TF) based audio watermarking methods. First, a motivation on the necessity of data authentication, and an introduction in Digital Rights Management (DRM) to protect digital multimedia contents is presented. TF techniques provide flexible means to analyze non-stationary audio signals. We have explained the joint TF domain for watermark representation, and have employed pattern recognition schemes for watermark detection. In this chapter; we introduce two watermarking methods; embedding non-linear and linear TF signatures as watermarking signatures. Robustness of the proposed methods against common signal manipulations is also studied in this chapter.