How it Happened

Robin snapped her fingers in front of his face, causing him to startle violently.

"Steve, are you even listening to me?" she asked, her expression twisted in clear annoyance.

Steve sighed, turning in his seat so he could get a better look at her mouth. Honestly, he was trying to drive. Couldn't she wait to talk until they got to work?

Or: Steve Harrington has lost the majority of his hearing. He just forgot to tell people about it.