While most drones do make quite a bit of noise there has been developments to make them quieter. Drones make a humming or buzzing noise from the sound of the engine and the sound of the propellers. Think about the sound your ceiling fan at home makes, except these spin a lot faster. The amount of noise depends what type of drone you own and its specifications.
Thanks to advances in technology there have been improvements in all aspects of drone specifications. Quadcopters for instance have four separate smaller engines rather than one large one. By utilising separate small motors for each propeller on a quad copter you not only get better stabilization but also reduce noise due to a phenomenon known as frequency spectrum spreading. Basically each of the propellers operates at a different RPM (revolutions per minute). As a result the harmonics are dampened and do not sound as loud as if all the engines were in unison or if you had one large motor instead of four smaller ones.
As with most things in life, you get what you pay for and generally the lower end product will make more noise than a premium model.
The ambient weather and amount of breeze will affect the amount of noise you will hear coming from your drone also. If you’re heading out to a drone convention and there’s numerous aircrafts flying around it’s sure to get quite noisy.
If you are considering using your drone for something like wedding photography for instance then you really do want to shop around and check out different models and compare reviews.
DJI has several ‘Phantom’ models which are marketed as a quiet drone. They’re a quality drone that has been designed with propeller stabilisers to reduce the hum made by the rotating blades. It also has internal motors which cuts the noise down again in comparison to models that have external motors.