You may think Scruffy is blessed with extrasensory abilities when he starts barking at noises you're unable to hear. It's probably not a poltergeist. The fact is, Scruffy's sensitive ears are capturing all sorts of sounds too quiet for you to hear, from critters living under your deck to a leaf blowing against the door. A trip inside Scruffy's eardrum explains how canines are capable of hearing sound.
Using Mobile Devices
As soon as your dog hears a noise, most likely his ears will shift to generate better reception. Controlled by at least 18 muscles, those furry appendages are highly mobile devices capable of rising, lowering, tilting and rotating to better capture faint sounds. If you're attentive, you may also witness Scruffy's ears moving independently of one another. This allows him to locate and focus on sounds coming from different directions.
Sound is waves of energy traveling along molecules in the air; hearing is the reception and interpretation of these waves. When sound waves reach Scruffy's ear drum, they're amplified by three small, sensitive bones known as the malleus, incus and stapes. Once the waves are transformed into electrical impulses in the auditory nerve, the brain registers the sounds. The ability to capture sounds is further amplified by your pooch's mobile ear flaps; indeed, by changing the manipulating the muscles within the ear flaps, Scruffy is better capable of catching high frequency sounds to route to his ear drums.
Scruffy's barking behavior may leave you wondering what his ears have captured. Before assuming he's responding to some supernatural event, consider the natural reasons for his uncanny ability to hear sounds. Scruffy's ear canal is much deeper than yours, and therefore creates a better funnel to carry sound to his eardrum. His ears are capable of detecting frequencies that are twice as high in pitch as those humans can perceive. When it comes to distance, Scruffy wins again; what you can hear from 20 feet, he can hear from roughly 80 feet.
Reacting to Noises
Because of the design of Scruffy's outer ear and the sensitive structures of his inner ear, he's capable of detecting noises in a different way than humans. This explains why Scruffy comes running to the noise of a silent whistle, which sounds at a frequency that humans can't hear, or gets excited upon hearing the bodily vibrations of termites in the walls. If Scruffy hates the vacuum cleaner, you'll have to blame its motor; it emits a screaming sound in the ultrasonic level, other than the familiar roar you're used to.
- Photodisc/Photodisc/Getty Images