Yeah, that's a good question. I think the latter parts of the battle when Superman went off to (spoilery stuff removed) indicate that they are just shockwaves from when she clangs them. During that section her and the uberDD were trading explosions with each other (it looked comical because the stuff around them like debris was getting tossed about). Since she did those without a 'triggering' blast that would seem to indicate no absorption is required. Loved the sound effects and sound design for those (it is HILARIOUS when they are trading) and they enhanced the message that DD had gotten more powerful due to the difference in duration and cadence