Why do vacuum cleaners make the characteristic noise that they do - what type of engine motor causes this?

It is NOT the electric motor creating that sound, it is the suction pump that is driven by the motor that is creating that sound while creating the partial vacuum that sucks in the dirt. If you have an upright vacuum cleaner, the beater brushes also make quite a bit of noise when you have them turned on when doing carpets.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.