1991 mercury capri, buzzing wont stop?

I have a 1991 mercury capri, made by ford, with a mazda race engine. You know how when a car door is open, and the cars on, it makes a buzzing/beeping sound? Wll my car wont stop making that noise, even though the doors are all shut, i cant seem to find a problem that could be causing it, or a resolution to make it better? help, please?