For humans, language sounds are fairly arbitrary. There is no set of words that have a common meaning for all members of our species. Many different sounds, in different languages, can mean the same thing. The sounds associated with the words, "perro," "chien," "Hund," and "dog," all mean the same thing, there is virtually nothing in common among the sound patterns which make up their words. The sounds that animals use to communicate with each other, however, have much more uniformity. These sounds are different for different species, but (except for certain regional "dialects" among birds) within any one animal type, there seems to be some sort of fairly common or universal language and there appears to be a universal sound code used by most animals. It is based upon three dimensions: the pitch of the sound, the duration of the sound, and the frequency or repetition rate of the sounds.
- The meaning of pitches: Low pitched sounds (such as a dog's growl) usually indicate threats, anger and the possibility of aggression. These are interpreted as meaning "Stay away from me." High pitch sounds mean the opposite, asking to be allowed to come closer or saying that it is safe to approach. The question is why should dogs, use and understand this Law of Pitch? The answer begins with the simple observation that big things make low sounds. For example, take two empty water tumblers, one large and one small and tap each with a spoon. The large one gives a lower pitched ringing sound. Obviously a dog does not change his size simply by changing the pitch of his sound signals. So, why would the receiver of this signal respond to these pitch variations at all, since they often do not represent the physical reality? Now here is where evolution and the development of communication begin to weave their magic. Suppose that you are an animal who is sending signals to those around you. Since you know that other animals are paying attention to the pitch of your signals you can now deliberately use that as a means of communication. If you want to make another animal move away, or to stay out of your territory, you could send a lower pitched signal, like a growl, suggesting that you are larger and more dangerous. Conversely you could also use a high pitched signal, like a whimper, to suggest that you are rather small, and therefore it is quite safe to approach you. Similarly, even if you are large, if you wish to signal that you intended no threat or harm when you approached another animal, you could indicate that you intended to act like a small harmless creature by whimpering or whining.
- The meaning of durations: Generally speaking, the longer the sound, the more likely that the dog is making a conscious decision about the nature of the signal and his next behaviors. Thus the threatening growl of a dominant dog that has every intention of holding his ground and not backing down will be both low pitched and also long and sustained. If the growl is in shorter bursts, and only held briefly, it indicates there is an element of fear present and the dog is worried about whether it can successfully deal with an attack.
- The meaning of frequency: Sounds which are repeated often, at a fast rate, indicate a degree of excitement and urgency. Sounds that are spaced out, or not repeated, usually indicate a lower level of excitement. A dog giving an occasional bark or two at the window is only showing mild interest in something. A dog barking in multiple bursts and repeating them many times a minute is signaling that he feels that the situation is important and perhaps even a potential crisis.
Barking is an alarm sound. There is no threat of aggression signaled by the dog unless it is lower pitched and mixed with growls. Let's consider the interpretation of the most common barks.