Hearing is one of the amazing senses that human beings and other animals have. We usually don’t pay attention to our hearing and how it works because, with time, it becomes one of the accepted things about life. But this doesn’t mean the process is simple.
Sound travels through the air in waves of different lengths. This is what causes various sound levels and frequencies. Our ears are designed to capture these sound waves so that the brain can process the information and let us know what is going on around us.
In nature, gathering this information is necessary for survival. Animals other than humans have developed extremely sensitive hearing as a way to determine if there is danger around. The outer part of the ear visible on humans and on many animals is responsible for gathering the sound waves, which are then funneled through the ear canal. (Compare this to an Earth-based satellite dish that “collects” signals.) The outer part of the ear helps us determine which direction the sound is coming from.
The sound moves down the tube known as the ear canal then comes in contact with the eardrum. The name of this crucial part of the ear tells us what its job is. The eardrum is like the tightly stretched “skin” on a drum. It vibrates when sound waves strike its surface.
Vibration of the eardrum causes three very small bones in the ear to move, causing the tiny amount of fluid in the inner ear to move as well. There are small hairs in the inner ear that bend in response to this movement and the nerves leading to the brain interpret this movement as an electrical pulse.
Yes, it is a complex and amazing process! Hearing is even more extraordinary because all of the movement of these tiny parts can be interpreted as completely different types of sound. In addition, similar sounds can be interpreted as having different wave frequencies (high-pitched screeches and squeaks as well as low, rumbling sounds).
Not only that, but the ear and the brain can interpret how loud a sound is. This is known by the term “amplitude.” Some animals have much larger outer ear structures than others so that they can determine source and direction of sounds much better than humans and other animals. Deer and rabbits, for example, have large, sensitive outer ear structures that capture even the slightest movement of sound waves in the air. This is essential to their survival.
Human beings have two ears that are isolated from one another (on opposite sides of the head). While humans have rather sensitive hearing it is nowhere near as sensitive as that of many smaller mammals. Some of these animals have huge outer ears that can rotate easily as they try to determine what sounds they are hearing. In addition to this, many animals have extremely sensitive inner-ear parts that allow them to hear sound frequencies humans cannot hear. This is true of dogs, for example. The complexity of physical movement that allows us to hear makes this sense one of the most amazing in nature.