Hi:
Most likely it is a swarm of bees has taken up residency some where in the walls. Contact your local bee association and they will know someone who will come and capture them. If you can't find the local bee assoiation cantact the county extension office I'm sure they can put you intouch with someone. There are many people (Bee Keepers) that would be willing to get the out for you it's just a case of finding one. Please, Please do not consider having the exterminated unless you have exahousted all possibilities of saving them and they are threating bodly harm. They do so much good for the areas gardens flowers and trees and many many other things of nature not to mention manfacturing the worlds best sweetner HONEY.

Wish I was close unough to help.
Barnabus