If you've ever wondered if it was coincidence that Sparky is so good at recognizing the sound of your car engine, know that it's not luck but good hearing. Not only can he hear higher frequencies, but he's better at distinguishing differences in pitch than you are.
Dogs' ears are physically positioned to receive sound: right up front, ready to listen. They're also engineered to hear a greater range of sounds than ours are. You can probably tell when something has caught Sparky's attention. His ears may perk up, he may tilt his head, or he may rotate his mobile ears for maximum effect.
Sparky's hearing range is quite different from ours, reaching a much higher frequency than we can hear. Hz, or Hertz, refers to sound frequency, the number of sound wave cycles per second. Humans hear between the frequencies of 20 Hz and 20,000 Hz; 2,000 Hz is the level we hear best. Sparky can't hear quite as low as we can -- his range begins at around 40 Hz -- but he can hear up to 60,000 Hz. His best hearing occurs at 8,000 Hz.
Sparky's entire ear works to provide him with sensitive hearing. His outer ear is important because he can respond to sound by adjusting the shape and direction of his hears to where sound comes from. The outer ear also includes the ear canal, which is much longer than ours and serves as an effective funnel to carry sound to his eardrum. The cochlea, in Sparky's inner ear, makes 3 1/4 turns compared to the 2 1/2 turns our cochlea makes, which is also thought to improve his hearing.
There's no solid evidence about why dogs need to be able to hear such high frequencies. The best answer probably rests with Sparky's ancestors, who had to rely on all their senses to survive in the wild. Dogs' keen hearing would be of great value in hunting and locating food, as well as alerting them to potential predators.
If you see any symptoms, such as bad odor, redness, swelling or discharge from Sparky's ears, contact your vet to be sure he keeps his keen hearing. You can clean dirty ears with a cotton ball dampened with hydrogen peroxide or mineral oil. Never insert anything into his ear canal. Frequent bathing or swimming can irritate his ears and lead to infection, so if Sparky's a water-loving dog, put cotton in his ears before he gets wet and dry his ears after water activities.