"está" is used for location, feelings, and states of being, while "es" is used for who, what, when, and where from (de donde es/son) kind-of statements or questions. And "esta" with no accent and "este" are used as the adjective form of "this", for example: "this chair"="esta silla" or "this desk"="este escritorio".
From what I've gathered, we use "es" when describing a state, something permanent. The professor on tje other hand is here now, at yhe moment, today maybe, either way it's not his permament place, so we use "está". The other explanation I've read was that always when talking about location we use "estar" rather than "ser"
The normal speed audio stopped at the end of the word "profesor." Please check this. I've had this problem since the beginning of the course.