More often than not I dont get a vocal response,usually they show up to check it out. Some will come right in and others will leave the area,I'm not sure if it scares less dominant coytes or what but it's been a proven killer for me over the past few years.
Also until fox season starts I'll use mostly coyote vocals,or atleast fire off one howl at first.It seems to keep most fox at bay instead of coming in to disturb my set......