Quieter Urban Air Mobility: Noise reduction with Propeller Positioning

What is it about?

Noise pollution due to flying vehicles has been one of the major problems for decades. Advancements in Urban Air Mobility (UAM) has brought a new concept of air taxis or Electric Vertical Take-Off and Landing (evtol) aircraft. On one hand, the air taxis are ready to take the market by storm. On the other hand, their architect of multiple propellers configuration will inevitably generate excessive noise level that can be disruptive in city environments. The paper first investigates the noise generation mechanisms for side-by-side propellers (a setup commonly used in evtols) operating under different combinations of rotating speeds and blade angles between them. It has also been observed that the noise level can be increased or decreased merely by changing the relative position between the blades of two propellers. This is achieved by a phenomenon known as the acoustical interference, where sound waves add-up with each other (constructive interference) or cancel each other out (destructive interference). The result in the article demonstrates a reduction in noise level when carefully setting the blades of two propellers at a certain angle.

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Photo by Hyundai Motor Group on Unsplash

Photo by Hyundai Motor Group on Unsplash

Why is it important?

The discussion in the paper is vital for developing quieter evtols, making them more acceptable for use in cities and helping to reduce urban congestion without adding excessive noise level. The research is crucial for the advancement and acceptance of UAM and evtol aircraft. By providing insights into how propeller noise can be effectively mitigated just by controlling the blade angles with respect to each other, the study addresses one of the major barriers to modern urban deployment. This is particularly significant in urban environments where residents are sensitive to noise pollution that could lead to public resistance and regulatory challenges. Moreover, quieter propulsion systems could enhance passenger comfort and urban liveability, making evtols more viable and appealing for widespread use. This research supports the development of efficient, effective, and environmentally friendly urban air transport, paving the way for a new era of urban mobility that alleviates traffic congestion without adding to noise pollution.