According to one embodiment, a noise reduction device includes speakers, microphones, and a processing circuit. The speakers are arranged around a rotor and emit control sound based on control signals. The microphones are arranged around the rotor and convert the control sound and noise emitted by the rotor into microphone signals. The processing circuit generates the control signals for reducing acoustic power in positions of the microphones, based on the microphone signals, rotation speed of the rotor, and a phase of noise that reaches the microphones from the rotor.

Methods, systems, and devices for active noise control associated with a mobile robot device are described. The methods, systems, and devices may include detecting ambient noise via one or more microphones of the mobile robot device, determining that the ambient noise satisfies a threshold by comparing one or more parameters of the ambient noise to the threshold based on detecting of the noise parameter, generating anti-noise based on determining that the ambient noise satisfies the threshold, and broadcasting the anti-noise in a first direction using one or more speakers of the mobile robot device.

A vehicle which includes a flight controller that is configured to receive one or more desired forces or moments associated with a plurality of rotors in the vehicle and determine a plurality of motor control signals for the plurality of rotors based at least in part on the desired forces or moments and an expected rotor noise produced by at least one of the plurality of rotors. The vehicle further includes the plurality of rotors, where the plurality of motor control signals is used to control the plurality of rotors.

An aircraft (100) with a rotary wing (40) is equipped with a propulsion system (10). The aircraft (100) includes a rotating mast (50) that rotates the rotor wing (40). The propulsion system (10) includes a pole (20) mechanically connected to the rotating mast (50) of the aircraft (100), where at least one end of the pole (20) is equipped with a motor (30) configured to rotate the pole (20) around the axis of the rotating mast (50) in such a way that the rotation of the pole (20) can be used to rotate the rotating wing (40). At each end of the pole (20) is placed a motor group (30), where each motor group (30) includes a pair of counter-rotating propellers (32,32), said pair of counter-rotating propellers (32,32) being arranged in such a way as to generate a rotational torque to rotate the pole (20).

A passive multi-frequency damping device for damping vibrations of an aircraft has a support structure, a plurality of N metal damping masses, each having a respective n-th mass, N being a natural number greater than or equal to 2, and n being a natural number from 1 to N, a plurality of N elastic elements each having a respective n-th stiffness, and each being glued to both the support structure and a respective n-th damping mass to support the respective n-th damping mass on the support structure so that the respective n-th damping mass is free to vibrate relative to the support structure. For each n from 2 to N, each n-th damping mass is arranged to at least partially surround an n1-th damping mass. The first damping mass has a solid semi-cylindrical shape, and the remaining damping masses have a hollow semi-cylindrical shape.

An active device for attenuating the acoustic emissions of an aircraft turbojet engine includes circulation conduits for a pressurized air flow rate supplying rotary elements each having a pulsation system for the delivered air. The rotary elements are controlled in amplitude and phase and deliver, to outlet diffusers, a pulsed air flow rate with a pulsation at the frequency of the noise to be attenuated having an amplitude and a phase adjusted according to a local feedback law with microphones to attenuate the radiated acoustic power.

Rotor noise cancellation through the use of mechanical means for a personal aerial drone vehicle. Active noise cancellation is achieved by creating an antiphase amplitude wave by modulation of the propeller blades, by utilizing embedded magnets through an electromagnetic coil encircling the propeller blades. A noise level sensor signals the rotor control system to adjust the frequency of the electromagnetic field surrounding the rotor and control the speed of the rotor. An additional method comprises of incorporating a phase lock loop within the control system configured to determine the frequencies corresponding to the rotors and generate corrective audio signals to achieve active noise cancellation.

A method of reducing noise generated by a tilt-rotor aircraft includes transitioning the tilt-rotor aircraft into an airplane mode from a helicopter mode, and reducing a speed of a first pair of fans of the tilt-rotor aircraft to be less than a speed of a second pair of fans that are positioned in-line with the first pair of fans. A flight control system configured to reduce a noise level of a tilt-rotor aircraft includes a flight control computer comprising a processor, a propulsion system communicatively coupled to the flight control computer, a first pair of fans and a second pair of fans communicatively coupled with the flight control computer and the propulsion system. The processor is operable to implement a method that includes transitioning the tilt-rotor aircraft into an airplane mode from a helicopter mode, and reducing a speed of the first pair of fans to be less than a speed of the second pair of fans that are positioned in-line with the first pair of fans.

An unmanned aerial vehicle (UAV) with audio filtering components includes a background noise-producing component, a background microphone, and a noise emitter. The background noise-producing component is configured to produce a background noise. The background microphone is positioned within a proximity sufficiently close to collect interfering noise from the background noise producing component. The background microphone is configured to collect audio data including the background noise. The noise emitter is disposed within a proximity sufficiently close to the background noise-producing component to reduce the interfering noise. The noise emitter is configured to emit an audio signal having a reverse phase of the audio data collected by the background microphone.

A system and method for reducing a psychoacoustic penalty of acoustic noise emitted by an aircraft, including a plurality of propulsion assemblies coupled to the aircraft, wherein each of the plurality of propulsion assemblies includes a motor, and a plurality of blades defined by a propeller, wherein the plurality of blades can define an asymmetric blade spacing; a control subsystem coupled to the aircraft and communicatively coupled to the motor of each of the plurality of propulsion assemblies, wherein the control subsystem is operable to rotate each of the plurality of propulsion assemblies at a different frequency to modulate the acoustic power distribution of the emitted acoustic signature.