To the [Department name] department:
Your constant loudness and jeering in the office haven’t escaped me. I appreciate the fact that you’ve made a close knitted second family out of your department. However, there is an appropriate time and place for everything.
While I don’t prohibit you from talking or making friends in the office, let’s us all remember why we come here every day. Work comes first before anything as long as we’re in the 8 hours that the company pays us for. Please focus on your jobs and avoid taking too much time with anything other than your tasks.
I hope to see great improvement on this.