"Excuse me, I need to go tell our students to try to be a little quieter, I figured a cinder block wall would keep most of their noise out... guess I was wrong." - Me while talking with a potential future employer who I had been trying to reach for 2 weeks.
On the upside, the person was amused by it. Unrelated to that I now have to set up a day to interview with them
TL;DR - when a mentor is on the phone is NOT a good time to play a team game of "whack each other with the pool noodles" in the room next to it. (Use the hall for that)