Wind power is one of the most important renewable energy because it is a natural energy source. However, wind power plants generate wind noise, causing damage to human body and livestock, radio interference, and pressure. Especially, low-frequency noise caused by Turbulence between the blade of the wind power plant and the wind is the biggest damage. Offshore wind power plants are becoming an alternative to minimize damage from wind power plants. In this paper, we tried to find out how the wave sound reduces the wind power plant noise by predicting how offshore wind power plant noise and wave sound are transmitted to nearby people. Experiment results in chapter 3, the wind power plant noise was 12dB larger than the wave sound, but the wind power plant noise propagated inland with a lot of sound attenuation from the sea. However, the wave sound was relatively less attenuated due to the sound from the coastline and propagated with many sound components. For nearby residents, the wind power plant noise, which is relatively smaller than the wave sound, is not heard. In addition, the wave sound with various sound components is mainly heard, giving a refreshing. As a result, it was confirmed that the wave sound reduces the wind power plant noise through the masking effect.