It is difficult to guess with no more context.

According to the glossary of the International Communications Union:

· screning frequencies: frecuencias de pantalla
· natural screening: pantalla natural
· electrostatic screening: pantalla electrostática

There several additional meanings for "screening", such as criba, cribado, verificación, etc., but I suppose "(de) pantalla" or "efecto de pantalla" is the best translation in that context.

Hope it helps!