Motor force...This link also has some useful info for the OP, and Oscar.
Thiele / Small parameters explained with real world cases
However Oscar's addition of the current is talking about "the force that the motor exerts"... and hence resistence does come into play.
(So I am not there is anything to suck?)
Basically the motor does not produce any sound when the I is zero.
And I assume that damping factor again comes into play as a possible theory for the OP?