A Dog's Sense of Hearing - The Basics

Most people know that canine's have an extraordinary sense of hearing. Historically, dogs have been known to rely on this sense for hunting prey and survival. Domesticated dogs are known to use the sense to alert the owner to something threatening in their environment. Aside from that, a lot of people don't know that a dog has such precision hearing simply because of the way their ears are made and how they work. Regardless of evolution or environment, the basics of how a dog's ear "hears" is as follows:

Beginning with the outside ear:

According to responsibledog.net, a dog's ear consists of four parts. The first part being the physical ear itself on the outside of the dogs' head, known as the pinna. Regardless of shape, size, position on the head, etc. these really are where a dog's sense of hearing all begins. The pinna has several muscles at the base of the ear where it attaches to the head that allow a dog to move their ears in many different positions together as well as independently of each other. While some may think their dog is simply trying to be cute, most often times a dog's ear responds to sound by first using the pinna to grasp the sound and hone in on it's location and origin. It's like a catcher's mitt with the pitcher moving around sporadically trying to pin point the exact location that the ball will land inside his glove. Once the dog "catches" the sound, the pinna then begins the process of sending the sound to the rest of the ear to complete the process of how your dog hears. This process is evident if one watches their dog closely. All we see is twitchy, fluttering ears and actually a message (sound wave) is being collected, sorted and sent on to the appropriate places.

Next Stop, The Outer Ear (Ear Canal):

This canal is located inside and is actually part of the pinna, close up to dogs' head. It is widely known that the ear canal in a dog is shaped like an L inside the dogs' head. Through this L, the sound travels down to the eardrum (tympanic membrane). This canal is simply cartilage that contains two different kinds of glands, which produce earwax to aid in the protection of the ear canal.

Now the fun begins, Inside the Middle Ear:

The eardrum separates the outer ear canal and the middle ear. Just beyond the membrane is where sound vibrations are transferred to the middle ear. Here eardrum vibrations activate the three tiny bones in the ear called the hammer, anvil, and stirrup. According to google image search results, these bones are the organs of balance inside the middle ear.Here sounds are processed and sent on to the inner ear in a manner so as not to cause damage to the inner ear due to too much sound vibration. This middle ear is also connected via the Eustachian tube to the mouth to allow for proper air balance inside the middle ear and eardrum.

Finally, The Inner Ear:

The inner ear is where all of the information is turned into what you know as your dogs' sense of hearing. This is where the vibrations from the three tiny ear bones of the middle ear are actually translated into electrical impulses that alert the dogs' brain to the noise and results in the dogs' ability to hear. Based on information collected from petplace.com, "The inner ear contains three distinct structures: the cochlea (spiral tube), vestibule, and three semicircular canals." In addition to being labeled as being "directly responsible for hearing" the cochlea is responsible for transferring those electrical impulses to the dogs brain. The vestibule and three semicircular canals are the organs for balance within the inner ear. Thus, allowing the dogs' brain to receive the information as to the position of the dogs' head.

One simply would not guess by looking at the dog that what is coming off as funny, perhaps flirtatious ear twittering and head cocking by your beloved pooch is actually a lesson in science going on each and every time, every single moment that you think your dog is being cute. Sounds are non-stop and never ending inside the dogs mind. What keeps them from going insane from it is their ability to channel that sound through the use of those ears that twitter and point hither and fro and decide which ones impose threat and which ones are acceptable or non-threatening. They possess the ability to turn off those sounds, through the use of the inner ear, that are non-threatening so as to hone in on what's at hand. Too bad humans couldn't possess that ability at times.

In addition to the basics of how a dogs hearing works, following are a few basic facts about a dog's sense of hearing overall.

A dog can pinpoint the origin of a sound within six-hundredths of a second. (1)

A dog's range of hearing is four times that of a human. (2)

Unlike humans, a dog's ear consists of approximately 18 different muscles allowing the dog to maneuver its ears in numerous directions. (3)

Dogs can decipher a sound of 35000 vibrations per second whereas humans only decipher 20000 vibrations per second. (4)

Sources:
Joyce D. Kesling, "The Canine Senses", Responsibledog.net
"The Brain And Senses", Google Image Search Result
Bari Spielman, "Structure and Function of the Ear in Dogs" Petplace.com
(1)"Dog Sense of Hearing Ear Problem In Dog", Guideofdog.com
(2)"Dog Sense Of Hearing", Seefido.com
(3)"Dog Anatomy", Wikipedia.org
(4)"Senses In Dogs", Pet-yard.com