vinceherman:
Easy enough to see if the noise is related to a weight bearing issue. Move the robot into position so that the servos whine.
Use your hand to gently lift the portion of the arm that the whining servo is supporting.
Does the whining change/go away?
Just tried that. No it does not.
MarkT:
PWM driven motors whine. Ultrasonic PWM can reduce/eliminate this.
Ah. After reading this, I saw a youtube video comparing the noise of a PWM motor vs ultrasonic PWM motor ( or lack of noise ). So I'll just need to find an ultrasonic PWM motor that matches with SR-431 and SR-311 PWM motors.
Is there any guide whether or not you can simply swap the PWM motor with an ultrasonic PWM motor ( assuming same power requirements ), and whether or not it can be simply swapped and attach to the same shield ? ( Sorry, not an electronics / electrical engineer ).