I gotta say...chams DO "hear." Whether it's vibrations or something else, they not only feel/hear that on vines but yes also in the air as well. I talk to mine all the time and whenever he hears my voice, he looks towards me and 3/4 of the time will even walk towards me. He knows my voice so well that if someone else speaks in the room, he notices it but shows WAY less interest. So yes they definitely do hear sound, even sound in the air.