Assessment of noise emission generated by helicopters using effective perceived noise level indicator. A case study

One of the elements of type certificate of aircraft is noise certificate. The article presents the method and results of certification tests for a helicopter with take-off mass exceeding 3175 kg. The performed tests involved 38 landing approaches, 51 overflights and 28 take-offs. For each test, the recorded data was analyzed in terms of acoustic signal (time history of 1/3-octave spectra), helicopter's flight trajectory, operating parameters (velocity relative to ground and relative to air, rotational speed of the main rotor) and meteorological parameters (wind speed, pressure, temperature, relative air humidity).