You unleash a wave of thunderous energy. Each creature in a 15-foot Cube originating from you makes a Constitution saving throw. On a failed save, a creature takes 2d8 Thunder damage and is pushed 10 feet away from you. On a successful save, a creature takes half as much damage only.
In addition, unsecured objects that are entirely within the Cube are pushed 10 feet away from you, and a thunderous boom is audible within 300 feet.
Using a Higher-Level Spell Slot. The damage increases by 1d8 for each spell slot level above 1.