The display is behaving normally and does not require service. What is happening is called Degaussing. Degaussing is the process of stabilizing the magnetic field of the CRT. It is a normal function of every display and does not indicate a need for service.
Waking the display from sleep or initiating a degauss from the on-screen display can also cause the same noise to be generated.
The viewable image size of the Apple Studio Display 17 is 16.0 inches.