Not sure what works?! About 5 years back I had a buck on a doe's scent and I grunted, whistled, and even said, "Hey!" Either that buck was deaf or he was seriously concentrating. I mean I YELLED HEY! Not even a flinch! Amazing.

But more seriously, last year I stuck 2 deer during bow season. The first one was walking kinda steadily from the woods to a field and was about 20 yards from me. Nothing stopping that deer so I let out a quick whistle. She stopped, I released and she went down shortly after. That worked. About 3 weeks after that I nailed an 8-pointer at 6:30AM on a cold morning before Halloween. He was walking slow, nose to the ground, etc. He walked less than 10 yards out and I grunted...."uurrrrrr"...he stopped and I stuck him good.

So, a gentle peep of a whistle to a grunt has worked. I practice my grunting and whistle even during my practice shooting, too.