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Quieter, Less Annoying Drones Are Coming

More and more drone manufacturers are looking to sedate the hum of their machines to improve the public acceptance of drones

Credit: Kaleb Kendall, Unsplash

Multiple studies have found that the annoying sound drones make is the biggest barrier to wider public acceptance of the flying robots – second only to concerns around privacy.


According to a NASA study, people find the buzzing sound of drones more bothersome than the lower-frequency loud noises of ground vehicles. Furthermore, research by the University of Salford in Manchester, UK concludes that drone noise is less preferable than that of commercial aircraft – even if it’s at the same volume!


So, in order to promote wider the adoption and commercialization of drones, more and more manufacturers are now looking to sedate the hum of their machines.


Impact of propeller design on drone noise


The noise level of drones is largely governed by the shape and design of their propellers. This is how DJI was able to achieve a staggering 60% reduction in noise power levels with the release of the Mavic Pro Platinum. And this is why you find many other drone operators going for aftermarket propellers designed to reduce noise.


A quick disclaimer here, though: Using a third-party propeller is one of the easiest ways to void the warranty of your drone and might even cause damage to the machine.


Machine learning to make propellers quieter


But what if drones had propellers that were actually pleasant to hear? Aerospace engineers at Australia’s RMIT University are working to make this a possibility. The team is using machine learning to design quieter propellers, the prototypes of which are then 3D printed for experimental acoustic testing.


And the results are impressive. The researchers have found that their prototypes produced around 15dB less noise than commercially available drone propellers.


There are two major factors at work here:

  • The numerical algorithms developed to design the propellers, and

  • The consideration of how noise is perceived in the human ear

Credit: Wix Media

Dr. Abdulghani Mohamed, aerospace engineer and lead researcher at RMIT University, says, “By using our algorithms to iterate through a variety of propeller designs, we were able to optimize for different metrics such as thrust, torque, sound directivity, and much more. We also formulated a new metric, which involves how the human ear perceives sound, and propose to use that in future designs.”


The team believes this method for optimizing propeller design can be applied to small quadcopters and flying taxis designed to carry human passengers alike. Mohamed goes on to explain how various manipulations of propeller blade noise can significantly impact how the human ear perceives it:


The modulation of high-frequency noise is a major factor in the human perception of rotor noise. Human ears are more sensitive to certain frequencies than others and our perception of sound also changes as we age. By designing to such metrics, which take into account human perception, we can design less annoying propellers, which one day may actually be pleasant to hear.

It’s worth noting that a quieter propeller design has been a key selling point for Joby Aviation, a passenger mobility company that has recently made its public trading debut on the New York Stock Exchange. The video below showcases how starkly different Joby’s propellers are from the deep, thumping sounds produced by a helicopter:


 

Ishveena Singh is a versatile journalist and writer with a passion for drones and location technologies. She has been named as one of the 50 Rising Stars of the geospatial industry for the year 2021.


In the last 13 years, Ishveena has worked with both mainstream media organizations (Miami Herald International, Times of India, Microsoft MSN) and dedicated geospatial technology media (Geospatial World, Geoawesomeness). With a deep understanding of content marketing and social media, Ishveena also helps private companies (DJI, Aerodyne Group, Terra Drone Corporation) to generate qualified leads through useful and timely content.

When she is not making magic at her desk, you are likely to find Ishveena on road trips, eating her way through life, or binge-watching TV shows. Connect with her today on LinkedIn and Twitter

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