I sometimes notice a slight crackling sound in my voice when speaking in a low register or humming.i can't tell if this is from mucus /sinus rattiling?

Hoarse voice: This is likely due to inflammation of your vocal cords. This could be due to post-nasal drip from allergy or upper respiratory infection. If this worsens or persist for more that a week then you should seek evaluation from your family physician.

Check it out: The best way to know what's going on with your voice is to have it exmined. A laryngologist can tell you more. It could be anything from mild dehydration to reflux to technique issues to a more serious issue. If your voice is bothering you, don't ignore it.