Whence comes the noise of a DC electric motor?

Factual Questions
1

In my tool collection, I have a Dremel, and a shop vac. Each uses a conventionally commutated DC motor. Each is also as noisy as hell. Why?

Is it:

mechanical noise from the brushes riding on the commutator

arcing at the brush-commutator connection

magnetostriction as the current in each winding loop is suddenly switched on/off when the brushes make/break contact

high-frequency torque spikes as each winding suddenly starts/stops making torque

…something else?

In fiddling with brushless DC computer fans, I have noticed that there is mechanical noise that is apparently related to the torque spikes of each stator winding being suddenly turned on/off resulting in jerky rotation of the magnetic field that drives the rotor (as opposed to the smooth field rotation one achieves in a synchronous AC motor). If I put a brushless DC motor of suitable RPM and power rating in my shop vac, would those torque spikes manifest as the same sort of noise that I currently see? Or would it run much quieter?

2

IMHO, most of the noise comes from the crappy bearings.

I’ve taken to lubricating the bearings in my Dremels when they get too loud, and it helps a lot. Also, there is a fan in the Dremel, and that probably makes quite a bit of noise, too.

3

I bet most of the noise is the rotation of the irregular core and windings, plus the little propeller, relative to the air. Like in a jet engine.