Many TFT and OLED panels today can produce sound unintentionally based on screen contents. This is mostly noticeable with repeating horizontal lines, which tend to produce whining at some fraction of the line frequency. Likely electrostiction.

This here seems to be about adding separate piezoelectric actuators to the display though, it doesn’t seem to use the panel itself.

> by embedding ultra-thin piezoelectric exciters within the OLED display frame. These piezo exciters, arranged similarly to pixels, convert electrical signals into sound vibrations without occupying external space.