Engineering Students Tackle the Noisy Problem of Urban Drone Use — and, Perhaps, Flying Cars

Natalie Reed, Matthew Walker, and Peter Sorensen, engineering students at the University of Cincinnati, have presented solutions to the noise problem of modern aerial drones — and suggesting the same technology could help user in the era of flying cars, too.

Aerial drones are incredibly useful devices, for everything from surveying and disaster recovery to photography and entertainment. What they are not, in their current form, is quiet: Even small drones have an audible whine, and as drones scale up so too does the noise pollution they generate. Take the technology to the logical conclusion of human-scale flying cars and autonomous delivery vehicles, and you have a real problem.

"I'm looking at noise from a societal impact,” explains Daniel Cuppoletti, assistant professor of the lab in which Reed, Walker, and Sorensen have been working to address the problem. "These vehicles have to be imperceptible in the environment they fly in or someone will have to take the brunt of that impact.

"One helicopter flying over your roof will keep you up. If you want 1,000 drones flying over cities in urban centers, noise will be a huge problem."

The solution, Cuppoletti claims, begins with testing on the human side: Using an anechoic chamber fitted with eight microphones to find out exactly what noises humans find annoying — and what noises various drone parts create.

Reed, to start, has been working on the positioning of rotors used on multi-rotor drone designs. "Changing the vertical gap influences the noise," she explains. "So I looked at what happens if we change the vertical or horizontal spacing." The answer: A variance in the noise generated of up to 10 decibels, enough to make a big difference in perceived noise pollution.

Sorensen, meanwhile, looked into whether rotation, counter-rotation, or a mixture would make a difference. Here, the results aren't as clear cut — "inconclusive," the University's press department admits. Details of Walker's work, meanwhile, have not yet been released.

The ultimate goal: a "guidebook," which drone manufacturers — and, perhaps one day, flying car manufacturers — can use to reduce the impact of their creations. "This is a very exciting time for aerospace," Cuppoletti claims. "New aircraft designs are at the preliminary and conceptual design stages. We can influence what they will sound like based on decisions designers make now."

Reed, Walker, and Sorensen presented papers on their work at the AIAA SciTech Forum; the papers have not yet been published for public viewing.