Although at times your dog's vocalizations might be unwelcome, those sounds carry much more information and meaning than you might think. In recent years many studies have investigated the noises made by companion dogs.
One major finding: dogs bark differently in various contexts, and it is possible to tell the difference. A 2004 study by Sophia Yin and Brenda McCowan in Animal Behaviour reported that “disturbance barks” (emitted in response to a stranger ringing the doorbell) sound different from “isolation barks” (when a dog is separated from an owner) and barks emitted during play. In each context, the acoustics differ: whereas disturbance barks are “relatively low-pitched, harsh barks with little variation in pitch or loudness,” isolation barks are “higher pitched, more tonal and more frequency modulated than the disturbance barks,” and play barks are “similar to the isolation barks except that they usually occurred in clusters rather than singly.”
Instead of seeing barks as meaningless noise, pay attention. Banjo might be yipping because he is alone, or he may have noticed that someone uninvited is climbing in through your second-floor window.
Dog barks are full of information, but what about growls? Anna Taylor and her colleagues at the University of Sussex in England found that, unlike barks, many acoustic properties of growls in a play and aggressive context are alike. But aggressive growls were longer than play growls, and play growls had a shorter pause between growls. Although growls from different contexts can sound similar to human ears, Tamás Faragó and his colleagues at the Family Dog Project at Eötvös Loránd University in Budapest found that growls carry considerable meaning in dog-dog communication.
In a 2010 study published in Animal Behaviour, dogs were placed in a room with a bone; as they approached the bone, researchers played a recording of one of three different types of growls. Dogs responded to the “this is my food” growl by backing away from the bone and, for the most part, ignored the “go away stranger” and the play growls because those sounds were not relevant to the bone. All growls are not the same, and dogs know it.
Even though not all growls are associated with aggression, an aggressive growl should not be ignored. If you come across a situation where growling could be a sign of aggression, keep your cool, though. Jolanta Benal, author of the 2011 The Dog Trainer's Guide to a Happy, Well-Behaved Pet (Quick and Dirty Tips), reminds: if you punish a dog for growling, you are essentially punishing it for giving a warning. Growling is a form of communication related to emotional or inner states in a particular context. If you want to decrease it, think about what is prompting it. The growling itself is not a problem.