Well, that was...one way to talk to a ghost, Natasha supposed. Then again, if they were supposed to keep the rainbows and unicorn poop present in their heads, then it made sense that tone of voice should also be welcoming and friendly. Still, she let Loki do the talking for now, remaining silent - she didn't want to drop her guard, but did a little, if only for the sake of easing into a more relaxed rapport with the spirit.
The sound of the footsteps made her turn, then the knock on the wall - or from within the wall? Nat went over to where the sound was, curious, touching gently to check for anything that might draw their attention. "Is that how you speak?" she asked, because tap code was certainly a real thing. It was different than Morse code, which she was also familiar with.