David's appearance to open this episode is very reminiscent of his comic book counterpart. Specifically the hair standing straight up and the red and black sleeveless jacket open over his bare chest.
It seems that the Division Agents doubled over when exposed to a certain sound. There are sonic devices which can injure, incapacitate, or kill an opponent. Moreover, a certain frequency called a "brown note" can cause someone to involuntary project bodily fluids from any cavity. One device in particular, a sonic cannon built by the LRAD (Long Range Acoustic Device) Corp. is being used by law enforcement and military personnel.