Watermarking is a basic secure communication method. It is used for embedding a recognizable pattern in media in such a manner that modification of the media also modifies the pattern, thus making it easy to detect the modification. This technique and its variants have many practical applications pertaining to secure communications, media verification, etc. Digital audio watermarking is a technique for embedding data within an audio signal in such a way that the original and the modified audio signals are essentially identical. The embedded data can be used for various purposes such as secure communication in military applications, owner identification and verification, content authentication, etc. In this study a watermark audio signal is hidden in a message audio signal by using a discrete cosine transform (DCT) domain approach. The tests of fidelity between the original and the watermarked signal and robustness applied to the watermarked signal. The results with both the Human Auditory System (HAS) and numeric/graphic aspects are presented. The results show that an embedded watermark is not easily detectable using either the HAS or other techniques. Additionally, it can be detected successfully in the simulation domain, but it may be susceptible to some noise and channel limitations in the real world.etc.