Abstarct: helicopter. The noise, which results from the motion of turbulent flow over the helicopter blade and its interaction with the media causes vorticity creation in a variety of different sizes, which is considered as one of the main sources of sound generation in a large range of frequency. In this thesis, the acoustics of helicopter blade is calculated by the aid of numerical simulation. for this aim, first, the turbulent flow field around blades is calculated using a turbulent model, then, the acoustics around the blades are modeled by using Ffowcs-Williams and Hawkings . The goal of this thesis is to investigate the sound propagating from helicopter blade to different distances, measuring the amplitude of propagation and also the effect of parameters such as the geometry on acoustic results. The obtained results show that in general, the noise amplitude of propagation decreases as the distance of observer location increases. Also in the blade’s axis-wise direction, it is observed that the maximum SPL is located at 20C, which might be caused by stronger vortices behind the blades. Furthermore, the numerical results illustrates that implementing a cavity in the mid-point of blade’s chord results in a reduction in noise generation. Although, it was found that using cavity near both leading and trailing edges has no impact on the reduction of noise generated by blades.