Voice students often have difficulty separating the sounds that they hear when they sing from what it will sound like to the rest of us. As anyone who has heard themselves on a recording knows, you sound very different in your own head. This can lead to singing in a way that sounds great to you, while it sounds "covered" or muffled to the rest of the world. Mental Floss has a great, short article on some reasons for this. Check it out. Why Do Our Voices Sound Different To Us Than To Other People? | Mental Floss.