Do Drones Make Noise?
Drones tend to emit a buzz that may pose a challenge when groups of delivery drones start operating in urban airspace. NASA’s GL-10 project has produced a solution to this problem of buzz sound in drones. The team developed the GL-10, which is the newest in a sequence of drone archetypes from NASA’s Langley Research Center in Hampton, Virginia. The archetype comes equipped with ten different engines meant to reduce drone’s trademark buzz sound, thus making the drone a little quieter. You would think that more propellers would make a drone buzz more, but NASA’s working principle is that numerous small propellers are quieter than a few large ones. Each motor on the drone operates at a faintly altered speed, which prevents the faint buzz sound combining into one loud buzz sound. The body of the drone is made from carbon fiber and has a wingspan of 3 meters.
More Engines Less Buzz Sound
The large number of engines, eight on the wings and another two on the tail, generate effective electric propulsion, but is also a solution to the problem of drone noise or buzz sound—numerous small motors produce less buzz sound than a few large ones.
The GL-10, which stands for ‘greased lightning’ can take off vertically. The employed silencing technology means that the drone is inaudible when flying more than 30 meters overhead.
Drones with less buzz sound are needed in situations like package delivery applications, where they need to be both quiet and safe. The employed technology that contributes to less buzz sound is called distributed electric propulsion. The drone also boasts innovative LEAP (Leading Edge Asynchronous Propeller) technology, which stops the buzz sound from the motors coalescing into one loud buzz sound.
Each Propeller or Motor Engine Can Be Operated At Slightly Different RPM
With the many propellers or motor engines, each is designed to be operated at slightly different revolutions per minute (RPM). The drone features a whole group of lesser harmonics and can be spread across the frequencies. This concept is called frequency spectrum spreading and is only possible because of the many propellers or motor engines and a high precision control of them. Since the GL-10 is inaudible and can take off vertically, it is ideal for urban parcel courier application. (See: How Do Quadcopters Work?)
Drones with Less Buzz for Package Delivery
Companies like Amazon and Google have certainly borrowed from this concept for their package delivery systems. Amazon is employing quieter octocopters that carry products weighing under five pounds to users, within 30 minutes of an order being placed. The drones are effective, quieter and safe being used as delivery vehicles. Google has held extensive tests of its own for drones to be used as delivery vehicles. In one successful test, Google flew cattle vaccines, dog treats, chocolate bars, water and radios to people in remote areas in Australia.
This drone technology would no doubt be borrowed by the military too, to be used in larger, manned aircraft which would match the size of the US Army’s missile-carrying Predator drones. This would help in providing a solution to the noise of the Predator and Reaper drones that patrol US war military zones, which is audible on the ground leading locals to realize drones are in the area.
Quieter Drones for Wildlife Monitoring
Quieter drones could be used to monitor wildlife without frightening them off, since some birds are sensitive to the buzz sound, and elephants flee from drones maybe because they perceive the buzz sound as that of a swarm of bees.