An aerial vehicle including a main body having a leading edge. An inlet is recessed aft from the leading edge. Forward protrusions extend from the main body on opposite sides of the inlet. An outlet nozzle is proximate to an aft end. The inlet is in fluid communication with the outlet nozzle. Wings extend from the main body.

This disclosure describes aerial vehicles and systems for altering the noise generated by the rotation of a propeller during flight of the aerial vehicle. In some implementations, propellers of the aerial vehicle are paired in a coaxially aligned configuration in which the pair of propellers both rotate in the same direction, are rotationally phase aligned, and separated a defined distance so that the noise from high pressure pulse of the induced flow from the lower propeller is at least partially canceled out by the noise of the high pressure pulse of the induced flow from the upper propeller.

An airfoil profile for an aircraft, such as an unmanned aerial system. The airfoil profile includes a leading edge portion and a trailing edge portion that are spaced apart along a chordwise direction, an airfoil centroid; and an upper airfoil surface and a lower airfoil surface. The airfoil surfaces are shaped such that the pressure center of the lifting force is arranged at the same chord location as the airfoil centroid or closer to the trailing edge portion along the chordwise direction than the airfoil centroid. With this, a pitch-down momentum is generated that urges the leading edge portion towards a lower angle of attack.

An airfoil profile for an aircraft, such as an unmanned aerial system. The airfoil profile includes a leading edge portion and a trailing edge portion that are spaced apart along a chordwise direction, an airfoil centroid; and an upper airfoil surface and a lower airfoil surface. The airfoil surfaces are shaped such that the pressure center of the lifting force is arranged at the same chord location as the airfoil centroid or closer to the trailing edge portion along the chordwise direction than the airfoil centroid. With this, a pitch-down momentum is generated that urges the leading edge portion towards a lower angle of attack.

Noises that are to be emitted by an aerial vehicle during operations may be predicted using one or more machine learning systems, algorithms or techniques. Anti-noises having equal or similar intensities and equal but out-of-phase frequencies may be identified and generated based on the predicted noises, thereby reducing or eliminating the net effect of the noises. The machine learning systems, algorithms or techniques used to predict such noises may be trained using emitted sound pressure levels observed during prior operations of aerial vehicles, as well as environmental conditions, operational characteristics of the aerial vehicles or locations of the aerial vehicles during such prior operations. Anti-noises may be identified and generated based on an overall sound profile of the aerial vehicle, or on individual sounds emitted by the aerial vehicle by discrete sources.

A vehicle, includes a main body. A fluid generator is coupled to the main body and produces a fluid stream. At least one fore conduit and at least one tail conduit are fluidly coupled to the generator. First and second fore ejectors are fluidly coupled to the fore conduit, coupled to the main body and respectively coupled to a starboard side and port side of the vehicle. The fore ejectors respectively comprise an outlet structure out of which fluid flows. At least one tail ejector is fluidly coupled to the tail conduit. The tail ejector comprises an outlet structure out of which fluid flows. A primary airfoil element is coupled to the tail portion. A surface of the primary airfoil element is located directly downstream of the first and second fore ejectors such that the fluid from the first and second fore ejectors flows over the such surface.

The present disclosure is directed to controlling, reducing, and/or altering sound generated by an aerial vehicle, such as an unmanned aerial vehicle (UAV), while the aerial vehicle is airborne. For example, one or more transducers, such as piezoelectric thin-film transducers, or carbon nanotube transducers may be applied or incorporated into or on the surface of propeller blades that are used to aerially navigate the aerial vehicle. As the propeller blade rotates and generates sound, the transducers may be activated to generate one or more anti-sounds that cancel, reduce, or otherwise modify the sound generated by the rotation of the propeller blade. The anti-sound combines with the sound and causes interference such that the combined, or net-effect, is an overall cancellation, reduction, or other modification of the sound.

An apparatus and method for reducing background noise captured by a UAV acoustic sensor are disclosed. The background noise may be reduced by incorporating a known UAV acoustic signature corresponding to a determined flight parameter into an adaptive filter coupled to the acoustic sensor.

Disclosed is a system for controlling acoustic radiation from an aircraft. The system comprising a plurality of rotor systems (one or more) and a noise controller configured to regulate acoustic radiation from the plurality of rotor systems. The noise controller can be configured to regulate a commanded flight setting from the flight control system and to output a regulated flight setting to the plurality of rotor systems. Based on the regulated flight setting, the plurality of rotor systems are configured to generate, individually and in aggregate, acoustic radiation having a target acoustic behavior. The target acoustic behavior may be achieved using beamforming techniques to, for example, change the directionality of acoustic radiation from the plurality of rotor systems, or otherwise tune the acoustic radiation to reduce detectability and/or annoyance.

An aerial vehicle including a main body having a leading edge. An inlet is recessed aft from the leading edge. Forward protrusions extend from the main body on opposite sides of the inlet. An outlet nozzle is proximate to an aft end. The inlet is in fluid communication with the outlet nozzle. Wings extend from the main body.