Yeah, I think we've talked about this before and decided that some versions DO say "voice of Windom Earle" ...but I don't remember if any of those were US versions and, if so, which media format they were.
Anyway... whether or not you believe Earle is actually the sender of that message, that is totally Ken Welsh's voice saying "I'm waiting for you." It seems kinda silly, incidentally, to think that Annie would send such a message... she doesn't even know who Briggs is.
It seems, rather, very logical that Earle would send the message to Briggs to taunt him into coming to Cooper's aid so as to have a final showdown of sorts with him. Earle is at this point drunk on the power of the lodge, thinking he can control it. i think he does have limited abilities while he's there, but he ends up pushing it too far when he does the soul-grabby thing.
Anyway; those are my two cents.