Can also use a piece of hose to help determine where the sound is coming from. Hold one end to your ear and mover the other end around to find the vicinity of the source noise. Direction finder!
Then use the dowel or screw diver or stethoscope to hear the noise with more 'detail' or 'clarity'.
After may years of vibration monitoring, trending and analysis, this sounds like gear noise. I expected 'higher pitch' to be more of a high pitched squeal, but from your video, not high pitched, but changes with speed.
I'd be checking the lash on the hook gear set.