You manipulate sounds waves in a 5 foot radius sphere centred on yourself to protect against eavesdroppers while allowing those within to converse normally. No sound can pass through the sphere; creatures within are immune to thunder damage from sources originating outside and are effectively deafened to everything not within the sphere, and vice versa. Until the spell ends or you dismiss it as a bonus action, the sphere moves with you, centered on you.

A successful Wisdom (Insight) check to read lips can still reveal what's said on the other side of the sphere.