Drones could soon make significantly less noise, as researchers at Australia&s Royal Melbourne Institute of Technology, together with aerospace company XROTOR, also based in Melbourne, have published a study demonstrating how significantly quieter (drone) rotors can be developed.
An important starting point for the research was the fact that human ears are more sensitive to certain frequencies than others and that this sound perception also changes with age. Central to the perception of rotor noise is the intermediate frequency modulation of high frequency sounds.
Different rotor designs generated by the algorithm.
The team used machine learning to design very different propeller prototypes, which were then produced via 3D printing and subjected to acoustic tests in a special anechoic chamber. The results are promising, showing that the best prototypes not only produce about 15 dB less noise, but also have a higher thrust profile compared to commercially available propellers.
Low-reflection test room
This success was made possible by two key innovations - the special machine-learning algorithms developed to design the propellers and the inclusion of noise perception in the human ear as part of the testing. The team was thus able to use algorithms to optimize a variety of propeller designs, taking into account various parameters, including thrust, torque and sound conductivity, among others.
The researchers hope to one day use clever design to alter the noise of the rotors so that they are even pleasant to listen to.