Overview of active and passive systems for the turboprop modern generation

Nowadays, one of the main marketing objectives of the new generation of turboprop aircrafts is the noise control to enhance the internal comfort. The propellers represent in fact the main noise source whose amplitude and frequencies depend on some design parameters such as its rotational angular speed, number of blades, power at shaft generating aircraft thrust and blades geometry. The higher energy levels are within the low-frequency region, corresponding in particular to the first blade passing frequency and its harmonics. The design goal is therefore to increase the passenger comfort level by controlling the propeller tonal noise and related vibrations. The present paper is aimed at discuss some relevant technological solutions to minimize the fuselage internal noise field at the passengers positions at each of the first three tones of the propeller load as well as due to other external aero-acoustic sources