Drone delivery is growing — along with noise complaints: who is trying to make them quieter, and how

The hum over the suburbs has become an everyday reality

Ashley Schmidt, a resident of a Dallas suburb, told BBC Newsthat she has almost stopped spending time in her own garden and has given up cycling to parks because of the sound of delivery drones flying over her house: 'You can hear the drones on approach, you can hear them inside the house when they pass right overhead, and you can hear them flying away.' Drone delivery, until recently a novelty, is becoming part of everyday life in the US: Amazon Prime Air is expanding delivery to nearly 500 cities and towns, and in some cities drones are carrying pizza and ice cream. Amazon's service has also launched for customers in the Darlington area of northern England.

Why drone noise is especially irritating

Antonio Torija Martinez, professor of acoustic engineering and psychoacoustics at the University of Salford, explains that drone sound is 'particularly noticeable, even when the overall noise level is relatively low.' Unlike aircraft, drones fly at low altitudes and can pass directly over residential areas, exposing communities that have never previously dealt with aviation noise. According to him, people react more sharply to a source they consider 'new, intrusive or frequent,' and those who themselves use delivery complain less. He warns that as the industry expands, complaints will only grow. In the US, commercial drones are overseen by the Federal Aviation Administration (FAA), which has been criticized for allowing noisy operations; the agency itself responds that primary responsibility for community problems lies with operators and local leaders.

Technological answers: shrouds and tipless propellers

London startup Greenjets has developed a propulsion unit that, according to the company, reduces drone noise by at least two-thirds: the rotating blades are enclosed in a shroud that muffles the sound and directs it away from the ground; rotor speed has additionally been lowered and materials that reduce vibrations have been used. The technology has already been used by police and port security services in Germany, as well as by conservationists in Africa tracking poachers from the air. Detroit entrepreneur Greg Sharrow came up with his idea in 2012, when he needed to film a violinist with a drone without noise: he found that the main sound is created by the blade tips, and designed a propeller with twisted, loop-shaped blades without sharp ends. At first this led to a quieter boat propeller; now Sharrow Engineering is developing 'ultra-quiet' drone rotors.

What the operators and the military say

Amazon said it has achieved 'measurable improvements in sound,' and that the new propellers on its drones 'produce almost half the perceived noise of the previous generation, with a softer tone.' Wing, which supplies aircraft for Walmart deliveries, says its propellers are designed to minimize noise and that flight routes are varied so as not to fly repeatedly over the same houses. In the military sphere, according to RUSI research fellow Robert Tollast, there is interest in low-noise drones — for example, US special operations forces are at the experimental stage — but for large drones in the Russia-Ukraine war, speed rather than stealth turns out to be the priority: 'Make it faster, not quieter — that seems to be the approach.' For Schmidt herself, there is only one acceptable solution: 'I would like them to stop completely until they figure out how to make their services stop being a nuisance.'

Image source, Amazon

Image source, Amazon

Image source, Greenjets

Image source, Sharrow Engineering