talk sb's head off
UK informal (US talk sb's ear off)
to talk to someone for a long time, usually loudly
She talked my head off.
— phrasal verb with drone verb
UK /drəʊn/ US /droʊn/
to talk for a long time in a boring way
He was droning on (and on) about his operation.
If you keep droning on like this, you're going to put your audience to sleep.
A: "The professor's already been droning on about polynomials for an hour."
B: "Oh, so that's why I lost interest an hour ago!"