His call is bracing but melodious, although once he sets to work on a blade, the noise of grindstone on metal brings out the old women with their beloved worn-out cleavers.

Then there's increasing the number of rotor blades. This helps because each additional blade carries less of the weight of the helicopter, and thus produces less noise.

It has been found that wake loss of the blade has a great impact on the performance and stability of Turbomachinery, and also has been recognized as one of main noise sources of Turbomachinery.