While Erwin is aware of Levi liking the sound of his voice, he has never realised just how much he likes it. He knows he has the power to get Levi to relax, and even fall asleep sometimes, just by talking, but he will likely never quite understand how it affects Levi on other levels. To him, it's just his voice.

Which manages to go up an octave or so when Levi starts rolling his hips forward, pressing against him. Erwin can't help the breathy little yelp that escapes, a sound decidedly less sexy than his poetry recitation. He's still very eager and very turned on, and getting that direct pressure is like a cool drink on a hot day. His hand falls to Levi's thigh and grips, holding there so he doesn't try to yank Levi up against him again.