something is probably stuck in it. Can you get your hand in and feel around? If this is just to yucky to contemplate, try it with a soft plastic bag on your hand, perhaps the kind used in the produce section of supermarket. Feel for something stuck in the grinding mechanism, and see if you can get it loose. Should I say that of course the disposal is not on at this time? If it is not connected to a dishwasher, there may be a capped section of pipe that can collect debri. Also, feel underneath the rubber gasket at the sink opening. After you have checked it well, try flooding it with water, fill the sink about half way up, and then run it, letting the water out. You can also sprinkle in baking soda, a half cup or so, and follow with a cup of vinegar, white or apple cider. It will foam up, but should have a deoderizing effect. Another trick is to run a lemon rind or even a cut up lemon through it. Good luck!