Like mobowhuntr said the weather, especially wind, has a lot to do with it. Box calls are IMO the loudest, then the slate, then diaphram. Wind will carry your call a long way, maybe 1/2 mi or better. Use the box or slate to get their attention, then finish it off with the mouth call, so as not to use more movement than you need to. When they get to where you can see them, you better not be moving when they are looking or you've lost your bird...[:'(]