Some Peculiarities of Helicopter Main Rotor Aeroacoustic for Far-Field ObserverAlexander Kusyumov, Sergey Mikhailov, Sergey Kusyumov, Elena Romanova and Georgios BarakosEPJ Web Conf., 213 (2019) 02048DOI: https://doi.org/10.1051/epjconf/201921302048