Although wolves use varied vocalizations to express themselves, if you ask anyone about wolf sounds, it's likely the howl that comes to mind. Howling helps keep family members (or pack-mates) together. Because a pack territory range over vast areas, it’s not unusual for members of the pack to become separated from one another. Wolves can call to one another over great distances by howling. A howl’s low pitch and long duration is well suited for transmission on the wild landscape – a wolf’s howl can be heard up to 10 miles away in open terrain! Wolves can howl to locate other wolves, advertise the size of their pack or territory, to warn other family members of danger using a bark howl, and more. Just like us, each wolf has a unique voice so distinctive features of each individual's howl allow wolves to identify each other. And when every member of the pack joins the chorus, the singular howls and their harmonies give the listener the impression that pack is larger than it actually is.
Howling isn’t the only vocalization employed by wolves. They also bark, huff, whine, whimper, yelp, growl, and snarl.
Also interesting, findings from a recent study suggest that wolf species have "howling dialects." Researchers used computer algorithms for the first time to analyse howling, distilling over 2,000 different howls into 21 howl types based on pitch and fluctuation, and then matching up patterns of howling. They found that the frequency with which types of howls are used – from flat to highly modulated – corresponded to the species of canid, whether dog or coyote, as well as to the subspecies of wolf. More via PHYS.ORG.