You could actually say it is sort of like chills, but without the physical response, just the mental one. It is just a general positive feeling that makes you feel, for lack of a better term, hypnotized. It is usually certain people's voices that do it to me, but only when they're not talking directly to me, such as lectures, TV shows, or a side conversation I'm not personally involved in. Do you ever find yourself listening to someone's voice, but not actually listening to what they say?