Abstarct: Detecting and tracking the target is a major part of control, security and military systems for avoiding collision with obstacles underwater or in the space. As for underwater target detection , detecting and tracking is difficult due to slow propagation of acoustic signals under the water and unwanted noise signals from environment and ships. In this thesis , underwater acoustic events are detected using passive sonar , baxsed on processing underwater acoustic signals emitted from the target. Once emitted , it's combined with background noise and simulated using wavelet filter detection algorithm. This passive detection and tracking system is studied in two different modes , first detecting a single target acoustic event and second detecting multi target acoustic event. In the end , wavelet filter containing noise energy spectrum is simulated using various simulations and is then compared to the wavelet filter without the noise energy spectrum. Which it's results shows that the filter containing noise energy spectrum has a better performance and less detection error compared to the wavelet filter without the noise energy spectrum