Take my answer with a grain of salt I'm far to be sure. But for what I know, the motor will create a sound with a fundamental (given by its rotation speed) and an infinite nb of harmonics, but they are less and less powerful whith their frequencies. Then you add a reduction gear that will create its "own sound", so un fundamental given by the motor fundamental multiplied by the gear ratio... and its infinite nb of harmonics (that are on the same frequencies if your ratio is an integer).

I guess the rotor blades will do something similar: you'll have the "primary sound" done by the motor (so its fundamental and an infinite nb of harmonics), _AND_ a sound generated by your blades, and seven blades certainly means that the fundamental of the blades is 7x fundamental of your motor fundamental, then its infinite nb of harmonics that fall on every 7 motor's harmonics.

I hope my explanation help you

The 7 bladed rotor will have a spectrum of frequencies, the fundamental being its rotational speed, i.e. one per rev. Other harmonics will be the multiples of 7. Subharmonics may be present due to defects in ball bearing.

A good question. I think you are asking about the blade-passing frequencies (BPF).

The BPF are mainly generated by the gap between rotor blades and the stator vanes. This is why BPF are treated in the design stage of the turbomachine. In your simulation, you have not included a stator, and therefore you the BPFs will not appear in your frequency spectrum. 

I would like to add that Blade passage frequency (BPF) will always be there as long as no of blades are more than one. Here BPF will be 7xrotational speed.