I pulled this article from allpredatorcalls.com its got some good info
While there are calls designed exclusively for bears, one can attract bears using common predator calls. The key to calling bears is to call non-stop until the animal is within firing range. When you stop calling, the bear will stop approaching. Some experts claim that calling will often attract sows more readily than boars. When you consider that sows often leave young cubs behind to come running to the call, you may inadvertently bring a sow with cubs into your shooting range. You should make it your practice to only shoot boars when you call.
One common misconception about calling bears is that if you make moaning sounds like a sow in heat, this would attract the boars. This is not true, bears are not a very vocal animal. It is not uncommon for a boar and sow to mate without making a single peep. Most communication in the bear world is between sows and cubs. But there are certain sounds that can peak a bear’s curiosity. The sounds of two bears bickering over meat is something that can draw a lot of attention.
Bear vocabulary is generally categorized in three levels of intensity:
1. Grunts. These are amiable, contented calls.
2. Blowing/chomping. These sounds are typically expressions of fear that include an explosive release of air, lip smacking and teeth clicking.
3. Human-like calls. This is where the vocabulary really expands. Some examples of Human-like calls include:
A. Moaning. The moan is a fearful call. A bear that’s been chased up a tree or a sow being pursued by a boar will moan if she’s not ready to breed.
B. Motor-like purring. Cubs make this sound when they’re nursing or they’re extra comfortable.
C. Pulsing angry sound. A sow may make this sound when trying to kick her yearling cub out of her territory.
D. Mother’s cry. A female may make this sound when she’s trying to locate her cub.
E. Cub distress call. This one sounds much like a human baby’s cry and is very attractive to sows.
F. Infringement call. The pulsing, angry sound made by an aggressive bear trying to drive another bear from his territory. This call can be effective near a food source in the fall.
Biologists caution hunters against using cub distress calls or any predator call that sounds similar to the cub distress call. Mothers will come to any sound that sounds remotely like a cub. Even the scream of a red-tailed hawk coming from far above has been known to make boars overreact. Females with cubs will apparently mistake rabbit-in-distress predator calls for the call of a young bear in trouble and will send their own cubs up a tree before investigating the crisis. A hunter could then mistakenly conclude that the bear has no cubs. If he shoots her, he ends up killing more than one bear.
Calling can be put to good advantage during the fall season. First and foremost you have to be where the bears are. A bear’s stomach determines where he’s going to be. Find a good food source in the fall – areas with good acorn or beech crops are prime – then use an infringement call, which is a type of a broken moan, which can be created by many of the reed bear calls.
Some hunters contend that sows do make moaning sounds when they’re in heat. They claim that you’re targeting mature boars that come to baits in the spring. They’re not necessarily looking for groceries. Since bait sites tend to concentrate black bears, boars tend to check them out in their search for sows in breeding condition. The sow moan is good conservation, since it helps hunters separate boars from lactating sows that may be nursing cubs at the time they’re using baits. Since adult male bears will kill cubs if given the chance, removing the big boys from the population helps to secure the future for the coming generation.
Standard rabbit-in-distress predator calls can also be effective on bears. But, unlike calling skittish and constantly paranoid foxes and coyotes, bear-calling requires a good set of lungs. It really is hard to overdo it. While the average fox hunter might call it quits after calling intermittently for 10 or 15 minutes, the bear caller should keep at it for 20 to 30 minutes. And unlike those sly wild dogs listed above, bears don’t tend to hang up just out of gun range. Just keep on calling and the bear will keep on coming.
If you continue your calling, don’t be surprised to find a bear standing six feet in front of you. It’s a sport that is definitely not for the weak of heart