Underwater noise caused by impact pile-driving during the installation of offshore foundations is potentially harmful to marine life. Therefore, in several nations (e. g. Germany, The Netherlands, Denmark, Taiwan, etc.), noise limiting values were developed to prevent injury of marine life. The experience over the last years shows, that underwater noise produced during pile-driving, depending on many parameters and measurements, and shows values, which exceed the national underwater noise limiting value by up to 20 dB. Therefore, Noise Mitigation Systems (NMS) are required to significantly minimize the underwater noise. Therefore, many different noise mitigation systems were applied during the last years during installation of Offshore foundations and were accompanied by underwater noise measurements in accordance to the ISO 18406. In this paper, a general overview of the existing and tested NMS, including various tested system configurations as well as combinations of different NMS, will be presented. Additionally, the achieved overall resultant noise reductions during pile driving as well as the factors influencing the noise reduction will be discussed. Moreover, it will be explored what implications the development towards larger foundations can have for the state of the art in noise mitigation.