Nine Heavy Waves technique

He didn't know what made these drums so mysterious. He just had to make one drum make a sound to pass the exam.

"HA!" Edward dashed towards a drum while condensing the Qi in his fist and randomly punched the drum.

"Doooonnnng" the drum made a muffled sound. Invisible sound waves were released from the clock drum which made Edward step back in shock.

"Huh?" Edward frowned. He dashed forward again and concentrated 5000 Jin of power in his fist then punched the drum directly.

"Dooonnnnngggg" a strong vibration spread throughout the atmosphere. The vibrations began to combine into a powerful wave. Once all the waves had combined into one the single remaining wave was launched directly back to Edward.

"Boooom" The powerful wave crashed onto Edward which knocked him into the air and sent him flying backwards.

"Cough, cough" Edward fell on the ground and coughed twice. Seeing the blood come out of his mouth stupefied him.

Edward's eyes stared blankly at the drum. He had just been attacked by the Nine Heavy Waves technique and that Nine Heavy Waves power was far greater than his own understanding. These drums were able to return attacks and duplicate the strength of the attacks they returned.

How intriguing. How did these drums return my attacks?

Edward was sitting and thinking deeply on the current situation. The first and the second time, he had only managed to make a muffled sound like a "dooong". The drums hadn't emitted anything close to a genuine drum sound on either of his strikes. To make things worse, the stronger his attacks were, the stronger they came back at him. It really was a mystery which seemed impossible to solve.