Noise Reduction Techniques for Drones

Ultra-quiet propeller and rotor systems for urban air mobility and quiet regional sky transit, comprising high-aspect-ratio blades with optimized stiffness and vibration damping, designed to minimize rotational and vortex noise through innovative structural features and operational strategies. The blades employ advanced materials and configurations, including spread-tow carbon fiber and carbon nano-fiber composites, to achieve maximum stiffness and vibration damping while maintaining low weight and drag. The system incorporates a synergistic approach to noise reduction, combining the Vortex Reduction Through Dynamic Stiffness (VRTDS) strategy with the Fibonacci Strategy, to achieve a comprehensive solution for ultra-quiet propulsion.

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Unmanned aircraft system (UAS) with reduced acoustic signature, comprising a multi-engine propulsion system where each engine is paired with a separate propeller, allowing for independent optimization of propeller design for noise reduction and performance enhancement. The propellers are optimized for minimum noise characteristics, featuring increased blade count, chord, and activity factor, while maintaining a lower rotational speed.

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A propeller design for unmanned aerial vehicles (UAVs) that improves efficiency, reduces drag, and lowers noise compared to conventional propellers. The propeller blades have a unique shape with a wider base and narrower tip, opposite to the traditional wide-tip design. This non-traditional blade profile allows higher lift and thrust generation with lower drag and noise levels. It addresses the issues of low speed, short endurance, and high noise levels in UAVs caused by traditional propeller blade shapes.

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A propeller for aircraft that reduces noise by optimizing blade design and motor selection. The propeller features a hub and blades with a unique sweeping portion at the tip, while the motor has a specific KV value of 720±72 revolutions/(minute·volt). The propeller is part of a power assembly that can be used in multi-rotor aircraft, where the rotation directions of the power components are different.

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Reducing the noise signature of multi-rotor aerial vehicles like drones by using different propeller designs on the vehicle. The vehicle has two motors, one for each propeller, with different propeller geometries that have different blade counts, shapes, or lengths. This spreads the noise across the spectrum rather than having large discrete tones, reducing perceived annoyance. The props are driven at the same RPM for hover flight to balance thrust. The system monitors prop RPMs and adjusts if needed to maintain balance.

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Method for controlling community noise from distributed propulsion (DP) aircraft by selectively controlling the relative phase (azimuthal blade positions) of each of the aircraft's individual propulsors. As the aircraft approaches a designated noise-sensitive area, an onboard flight controller automatically directs propulsor noise away from the area using input from a phase generator module, with the phase generator module purposefully varying the respective phases of the propulsors to meet an acoustic target. This allows reducing noise levels at sensitive areas without requiring alternative flight paths.

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A noise reduction system for aerial vehicles, such as VTOL aircraft, that dynamically adjusts motor fan RPM and pitch to minimize noise levels while maintaining sufficient lift and safety margins. The system identifies optimal operating parameters based on vehicle noise characteristics, ambient noise levels, and environmental conditions, and sends commands to the motor controller to implement the optimized settings.

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A noise reduction system for aerial vehicles, such as VTOL aircraft, that dynamically adjusts motor fan RPM and pitch to minimize noise while maintaining lift and safety. The system identifies optimal fan settings based on vehicle noise characteristics, ambient noise levels, and environmental conditions, and sends commands to the motor controller to implement the optimized settings.

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A system for mitigating noise signatures of vertical take-off and landing (VTOL) aircraft in urban environments. The system receives flight requests, accesses aircraft noise data, and determines optimal routes and flight parameters to minimize noise impact. Real-time noise monitoring and predictive modeling enable dynamic adjustments to aircraft operations, such as speed and propeller usage, to manage noise levels and optimize flight paths.

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A control system for unmanned aerial vehicles (UAVs) that dynamically adjusts flight paths and operations to minimize noise pollution. The system acquires noise level allowances based on time, altitude, location, and weather, and controls UAV flight accordingly. It can also vary article transfer methods, control propulsor operation, and select power sources to optimize noise reduction.

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Noise suppression technique for autonomous devices like robots that can adapt to changing noise sources as the device moves. The technique involves using a beamformer with fixed and adaptive components to selectively isolate desired audio and suppress noise. The fixed beamformer suppresses noise from known directions based on filter coefficients. The adaptive beamformer identifies and removes noise from moving sources by detecting relative motion. This allows the device to adapt to changing noise sources as it moves.

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Reducing noise from unmanned aerial vehicles (UAVs) in recorded audio by leveraging state information about the UAVs. A microphone on the UAV picks up audio including both the desired sound source and UAV noise. The noise reduction involves a processing unit that reduces the UAV noise based on information like motor speeds, wind conditions, and position estimates of multiple UAVs. This allows more accurate estimation and cancellation of the UAV noise compared to just using the audio input.

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A sound processing method for unmanned aerial vehicles (UAVs) that enhances audio quality by leveraging dual-microphone noise estimation. The method collects sound signals from two microphones, one capturing the desired audio and the other capturing the UAV's noise, and uses the noise signal from the second microphone to estimate and subtract noise from the first microphone's signal, resulting in improved signal-to-noise ratio.

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Active noise control for drones to reduce the noise they generate while flying. The method involves adjusting the shape of the propeller blades mid-flight to alter the frequency and amplitude of the sounds they make. This is done by actively controlling the joints in the blades to change their shape. By coordinating the blade shape changes across multiple propellers, the total sound generated by the drone can be cancelled, reduced, or altered. A trained machine learning system determines optimal blade shapes for different environmental conditions, operational characteristics, and locations to generate anti-sounds that cancel out the drone's original noise.

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Active, predictive noise cancellation for reducing the noise emitted by aerial vehicles like drones. The system uses machine learning to predict the noise levels and frequencies generated by the vehicle in specific operating conditions. It then emits anti-noise at those levels and frequencies to cancel out the predicted noise.

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An unmanned aircraft with reduced noise impact on sound processing targets. The aircraft has rotor blades shrouded in a duct. The duct's inner space has a minimum height to width ratio of 0.5. This geometry creates a quiet area that reduces rotor noise. The aircraft identifies this quiet area and uses it for sound processing tasks like recording or outputting sound.

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Acoustic system for urban air mobility (UAM) vehicles like air taxis to reduce noise compared to traditional helicopters. The system involves a shroud around the rotor blades with a perforated inner wall and enclosed chamber. The perforations allow sound to enter and resonate in the chamber, reducing noise transmitted through the shroud. The chamber walls can have an acoustic liner. The shroud geometry and chamber depth can be optimized based on rotor frequency for noise reduction.

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A noise reducing shroud for unmanned aerial vehicles (UAVs) that helps minimize noise produced by the propellers. The shroud is designed to reduce, absorb, and diffuse sound waves. It has a body that encloses the propeller and an interior surface with baffles that reflect and refract sound energy to dissipate it. The shroud also uses sound absorbing materials to further reduce noise.

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Unmanned aerial vehicles (UAVs) that operate in cluttered environments achieve reduced noise emission through optimized ducted fan design. The system incorporates a noise-reducing duct with strategically positioned acoustic absorptive materials, modified intake and outlet openings, and rotor mounting configurations that minimize pressure wave generation. The ducted fan design enables efficient thrust while minimizing noise signatures, particularly in environments with high rotor density. The system enables autonomous navigation and image capture capabilities in cluttered environments.

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Aerial vehicle with integrated acoustic panel for noise reduction. The vehicle features a fuselage, pylon, and specially designed acoustic panel that incorporates sound-absorbing materials to minimize external noise. The panel is strategically integrated into the vehicle's structure to effectively attenuate sound waves, particularly in the high-frequency range relevant to aircraft noise.

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