Some hunters slam car doors, blow air horns, and use other unnatural sounds to shock birds into gobbling. Such noises put pressured toms on the alert even as they make them gobble. As a hunter, you'll feel more confident if you can make natural sounds in the woods to draw gobbles from an unseen bird. All of them work some of the time. The sharp, high pitch of a crow call often draws gobbles when hoots don't work.
Many hunters prefer to owl call early in the morning and use crow callers after the sun is up.
Coyote howlers are very effective for roosting turkeys in the evening, as are gobble shakers. Sometimes that unusual sound will draw a gobble from jaded birds who have heard too many hoots and caws during hunting season. If the turkeys will gobble on their own, don't risk drawing extra attention to yourself by making any noise. Hoot too loudly to a nearby turkey, and you may blow him right off the roost. Start with soft hoots and work your way up the volume scale.