Amazon's Drone Buzz Triggers Backlash — and a Race to Build Quieter Rotors

Amazon Prime Air is expanding drone deliveries to nearly 500 cities and towns — and residents like Ashley Schmidt are already retreating indoors because of the noise. "They emit this very annoying buzz. It triggers my fight or flight response," says the 44-year-old administrative assistant from North Garland, a Dallas suburb.

Schmidt no longer spends much time in her garden and has given up cycling to local parks where she photographed bugs, lizards and toads. "You can hear the drones on approach and you can hear them inside your home when they pass directly overhead and then you hear them as they leave," she says.

Why does drone noise cut through when traffic doesn't?

Even in noisy cities, drone whine stands apart. The sound tends to be "particularly noticeable, even when overall sound levels are relatively low," says Antonio Torija Martinez, professor in acoustic engineering and psychoacoustics at the University of Salford.

Unlike planes, drones fly at low altitudes directly over residential areas. "They can expose communities that have not previously experienced significant aircraft noise, and who may therefore be more sensitive to changes in their local soundscape," he says.

His research shows people respond strongly to noise they consider "novel, intrusive or frequent" — and those who benefit from drone delivery tend to be less bothered. Complaints will spread: "At the moment we are seeing some of these problems localised in some areas, but… as the drone sector expands, more and more of these complaints will happen," he warns.

Who regulates the noise?

The Federal Aviation Administration regulates US commercial drones but has drawn fire for permitting noisy delivery operations. The FAA says operators and local community leaders hold primary responsibility for addressing community concerns.

Can technology muffle the buzz?

London-based startup Greenjets designed a propulsion system it claims cuts drone noise by at least two thirds. The company tackled "noise level and the frequency of that noise," says Darren James, future technologies lead at Greenjets.

Standard propellers slice through open air, creating the high-pitched buzz. Greenjets encloses spinning blades inside a pod to muffle sound and direct noise away from the ground. Slower rotor speed and vibration-damping materials quiet things further.

The tech has already found quieter-minded customers: police and harbour security teams in Germany, and conservationists in Africa tracking poachers from above without being detected.

What about the military?

Battlefield operators want stealth too. "There are some efforts to reduce the sound of drones. The US Special Forces are interested, at an experimental stage," says Robert Tollast, research fellow at the Royal United Services Institute (RUSI).

But speed beats stealth for larger drones in the Russia-Ukraine war. "Make it faster, not less quiet, seems to be the approach," Tollast says.

What did a violinist teach drone designers?

Detroit entrepreneur Greg Sharrow's quest began in 2012, filming a classical performance from a tricky angle. "I knew that most of the noise from the drone was coming from the propeller, not the motor," he says. The blade tips, swiping through air, made the noise.

"I asked myself a very simple question, what would a tipless propeller look like and how would it function?"

The answer: twisted loop-shaped blades with no points. Testing proved easier in water, so Sharrow first built a quieter boat propeller. His company, Sharrow Engineering, now develops "ultra-quiet" drone rotors. "We have validated that the technology works in drone applications and that it is dramatically quieter," he says.

Are the delivery giants responding?

Amazon says it has made "measurable sound improvements" — its latest custom-designed propellers "produce almost half the perceived sound of the prior generation, with a milder tone."

Wing, whose vehicles serve Walmart deliveries, says its propellers minimise noise and its flight paths vary to avoid repeatedly overflying any single home.

For Schmidt, none of that goes far enough. "I would like them to completely stop until they figure out how their services stop being a nuisance," she says. With Prime Air live around Darlington in northern England and pizza and ice cream drones taking off in US cities, quieter rotors are now the sector's race to run.