You must have experienced the result of your dog's super hearing ability. You are sitting in your favorite chair reading or taking a nap, with your faithful pet lying at your feet. It's blissfully quiet – not a sound to be heard. Suddenly your dog leaps to his feet and begins barking loudly, his protective bark, and you run to the window to see who is approaching. But there's no one there. At least not at first. It takes moments before someone actually comes into view and walks by the house or into the yard.
The dog's ability to hear is incredibly acute compared to humans. They can hear sounds over a wider range of frequencies and a greater distance than we can. Also, experiments have shown that a dog can locate the source of a sound in about six-hundredths of a second. Their highly mobile ears capture sounds and funnel them down to the eardrum. You might see your dog cock one ear to capture the initial sound, and then use both ears to catch the maximum number of sound waves. Protection and guard dogs use their sense of hearing, along with their sense of smell, to detect possible intruders, sometimes from great distances.