Analog servos are quieter than digital. Servos have a feedback potentiometer that tells the servo chip the position of the servo arm. If it's not in the right position, it will try to force it back. If something's pushing it, it will push back.
When a servo is perfectly centered, it will not try to move the arm and thus be quiet. But if a tough hinge is pushing or pulling on the control rod, it will make a slight buzz. When you apply more force to it, it will make more noise. When you reach the maximum force of the servo, it will either strip a gear or stall - meaning it draws a lot of current.