Your puppy's ears are sensory organs of hearing, and also provide a sense of equilibrium, or balance. Canine hearing is remarkably acute; it's used in hunting, protection, and play, and is an important tool that keeps dogs in touch with their world.
Puppies are born virtually deaf. Their ears and eyes are sealed at birth so they rely on vibration and scent for this period of life. Even though the ears and sound detection are not yet fully functional, the balance function of the ears allows the babies to move about, recognize when they tip over and struggle to right themselves. Once the ears become unsealed at about two weeks of age during this early puppy development, and the baby dog learning to recognize and react to different sounds.
Canine Ear Structure
The structure and function are categorized as the external, middle, and inner ear. The visible portion, called the pinna, is a triangular cartilage flap covered on both sides by skin and fur. The size and shape varies among breeds. Some are erect (prick ears) like the German Shepherd Dog, folded to some degree (drop ear) as in the Collie, or pendulous as in Cocker Spaniels. The pinna of some dogs is surgically altered by cropping to conform to a breed standard.
The pinna is extremely mobile, with more than twenty separate muscles that provide 180 degrees of movement. This mobility helps collect, capture and direct sound further into the organ. It also aids in canine communication by offering a host of expressive ear positions.
The pinna funnels sound down the L-shaped auditory canal. This configuration, a vertical passageway ending in a right-angle turn inward (the foot of the L), helps protect interior structures. However, it also makes dogs prone to ear infections when debris collects in the foot of the L. Hair that grows in the ears of a number of dog breeds may compound the problem.
How Puppies Hear
Sound waves pass through the auditory canal, and strike the tympanic membrane, or eardrum. The resulting vibration is passed to a chain of three tiny ossicles (bones called the hammer, anvil and stirrup) of the middle ear. The eustachian tube which helps equalize pressure within the ear is also located in the middle ear, and connects this area to the back of the throat.
Vibrations are transmitted by ossicles to the inner ear, a bony chamber containing four fluid-filled organs responsible for hearing and balance. Chalk-like particles float in the fluid inside the semicircular canals, utricle and saccule, and as the dog moves his head they brush against tiny hairs that line these organs. That signals directional information to the brain, and gives the dog his sense of equilibrium.
Sound vibration is read by the fluid-filled cochlea, a snailshell-like coil of tubing lined with a membrane called the cochlear duct that spirals its length. The "organ of Corti," a specialized area of this lining, is where hearing actually takes place. Vibration-sensitive hairs that cover the organ of Corti pass information through the auditory nerve to the brain, where the vibration is interpreted as sound.
These intricate organs enable your dog to hear sounds you cannot detect, particularly at high frequencies and at soft volumes. People are able to hear low-pitch tones about as well as dogs, but while we typically hear sound waves up to 20,000 cycles per second, dogs may hear frequencies as high as 100,000 cycles per second. The size of the dog doesn't matter, with Chihuahuas able to hear just as well as Great Danes. However, age tends to temper the dog's hearing, and young dogs hear better than old dogs.