Callin' and killin' a coyote with a bow is a challenge, for sure. Getting the sound away from you/bow shooter will certainly help. A decoy with movement will help. Not so sure the stationary coyote decoy will help, from what I've seen and heard is that a coyote will usually stop its approach once it spots the decoy, or it will start to swing downwind once it spots the decoy.
Just need to plan on calling in several coyotes before it all comes together. The movement of getting drawn is something that hardly goes un-noticed by most coyotes.
I also like the expandable broadheads that offer 1.5" of cut to get as much blood pumped out as possible. Them suckers can go a long ways when hit and that fur soaks up blood like a spunge.
Good luck and post the story and pics. if ya succeed!