Thor cannot whisper.
He genuinely believes he is whispering because, by Asgardian standards, he's being quiet. Steve will be trying to sneak around somewhere and Thor will lean down and loudly whisper:
“STEVE. I BELIEVE WE SHOULD BE LEAVING NOW.”
Steve: “Thor. That's not a whisper.” Thor, genuinely confused: “I lowered my voice.” He also gets offended when everyone else can hear him coming from three rooms away because he insists he is being “quite stealthy.”

















