It really amazes me sometimes! Her big thing recently has been pointing to her ear when she hears something and making a question sound to ask what it is. Or sometimes she will tell me what she thinks it is; for example, pointing to her ear and saying "dog" or "car".
Yesterday she asked me what a sound was. It was a car door closing outside. When I told her that, she said "Da!" because she thought it was Lee coming home.
And this morning she did a different thing with her ear. She cupped her hand over her ear and she made a sound like static. She was hearing Jackson's white noise machine over the monitor (we turn the monitor up pretty loud so we can be sure to hear him if he makes noise) and wanted to know what it was.