Active device for attenuating acoustic emissions for a turbojet engine including controlled turbines

An active device for attenuating tonal acoustic emissions of a nacelle of an aircraft turbojet engine, the active device comprising:

• a circulation conduit for supplying controlled pressurized air flow;
• and
• a rotary element receiving the supplied controlled pressurized air flow, wherein the rotary element comprises a chopping system for pulsating the flow of delivered air, wherein the rotary element is controlled in speed and in angular position, wherein the rotary element delivers to a diffuser at an outlet of the device a pulsed air flow rate with a pulsation having an adjusted frequency, phase, and amplitude so as to reduce acoustic power radiated out of the nacelle, wherein
• the rotary element comprises an outlet sleeve, wherein the outlet sleeve has an adjustable passage geometry for the output air flow rate.