I own a table that uses a Hurst motor and had done some tweeking which involved pushing the pulley down on its shaft which ended up pushing the armature against the bottom cap of the motor housing which made a sound not unike what you're describing. I was able to reposition the spindle/armature within the housing with little effort and take care of the problem.
Rest assured that even inaudible resonances of the motor are affecting the sound although you won't know it until you get rid of them.
Rest assured that even inaudible resonances of the motor are affecting the sound although you won't know it until you get rid of them.