@JeremyECrawford When silence or a similar non-visual area of effect is created, should it be clear where the boundaries are to players (and NPCs) who didn't cast it?
— PigFiend (@PigFiend) November 7, 2018
The boundaries of a silence spell are only clear to you if you cast the spell, you magically detect it, or you notice the lack of sound and discern the extent of the effect (by walking through it, for example). #DnD https://t.co/z2sAOD1TZ3
— Jeremy Crawford (@JeremyECrawford) November 8, 2018