The anechoic measurement is done in an anechoic chambre, or sound room, the other measurement is "in room" which will be closer to what you would get in your own home environment. Have a look on Axiom's site, you'll find some articles about their anechoic chambre as well as some pictures of it. It is a replica of the NRC's anechoic chambre in Ottawa.

Half of communication is listening. You can't listen with your mouth.