Well, the door that shuts for internal re circulation is insulated so that could be masking the noise. As for an electric servo, there isn't one that I can think of. Everything back there is vacuum operated, so maybe you are only hearing the noise through the vent? If you want a good look at what's there, press the pins on the sides of the glove box and let it drop. You'll get a good look at what's mounted on the box.
The only relay that's back there that I can think of is attached to the top of the EEC bracket, although I'm not sure what it's for.