Locked room, loud noise

"What was that?" Rong Wei woke up and questioned. His eyes warily looked around the room but he did not find anything. However, he was sure that he heard something just now! 

Captain Lei also stepped down from his bed. He was looking at the direction from where the sound came from but there was nothing but a wall! Did the sound come from the room next door? 

"It must be the kids," Yun Yi yawned and then turned to the other side of the bed. He said, "There is no need for you to worry." Yan Shan agreed with him, the children living in the room next to them must have dropped something on the floor. It was three in the morning, it was normal to drop something while moving in the darkness. 

There was no need to worry.