This article presents an approach to build and verify a tool for calculating aerodynamic noise characteristics of helicopter rotors. The calculation tool is built on the basis of combining the vortex lattice method and the Formulation 1A of Farrasat, which is one of solutions of the Ffowcs Williams-Hawkings (FW-H) equation. By comparing the obtained result with data from reputable international publications, the calculation tool is verified for accuracy and reliability. The variation and value of the acoustic pressure from this calculation tool are in a good agreement with the international published works. Applying the tool in some specific calculation cases gives appropriate results, thereby giving important recommendations about the safe distance corresponding to the human hearing threshold for rotors with specific geometric dimensions and operating characteristics.