The "sound that explains everything" is the 5 seconds of the trim wheel running. When I am next working I will have a look how much of the trim range 5 seconds of trim at high rate covers, but I would guess it is not far off half the total trim range.
Not a 737 but now called a "Boeing": my trim runs at 0.3°/per second. Video it with your phone... on the ground.
I also get a "Stabiliser Motion" call from "Patricia" if the trim runs continuously more than 1 degree.