curious

    This is a question for those that I know personally (i.e. face-to-face), though the rest of you may find it curious as well.
    What is it about my voice that makes it so difficult to understand? Do I just mumble? Or do I speak too softly? Or is the tone of my voice just so...odd...or 'off', that it is indistinguishable from background noise? I know that I can make myself heard and understood, but an inordinate number of my conversations involve the words, "Excuse me?" or "Pardon me?" or "What?", and me repeating myself - generally repeating something inane and better left unsaid in the first place.
    No one's really complained, and it hasn't come to a head. I'm just wondering.