I would talk to my principal and explain what whole brain teaching is all about and the wonderful changes you are seeing in your students. Explain that your room may be little bit loud due to all of the activley engaged learners, but don't mention the complaints. With principal support, you will be in a good position when complaints travel farther than your ears.
Keep your door shut and when the librarian complains again, sweetly say 'thanks for letting me know.' and leave it at that.
You could also put a sign by your door like the one I have that says "Death is silent. Learning is noisy." It makes people think.