To understand how your ears hear sound, you first need to understand just what sound is.
An object produces sound when it vibrates in matter. This could be a solid, such as earth; a liquid, such as water; or a gas, such as air. Most of the time, we hear sounds traveling through the air in our atmosphere.
When something vibrates in the atmosphere, it moves the air particles around it. Those air particles in turn move the air particles around them, carrying the pulse of the vibration through the air.
To see how this works, let's look at a simple vibrating object: a bell. When you hit a bell, the metal vibrates flexes in and out. When it flexes out on one side, it pushes on the surrounding air particles on that side. These air particles then collide with the particles in front of them, which collide with the particles in front of them, and so on. This is called compression.
When the bell flexes away, it pulls in on the surrounding air particles. This creates a drop in pressure, which pulls in more surrounding air particles, creating another drop in pressure, which pulls in particles even farther out. This pressure decrease is called rarefaction.
In this way, a vibrating object sends a wave of pressure fluctuation through the atmosphere. We hear different sounds from different vibrating objects because of variations in the sound wave frequency. A higher wave frequency simply means that the air pressure fluctuation switches back and forth more quickly. We hear this as a higher pitch. When there are fewer fluctuations in a period of time, the pitch is lower. The level of air pressure in each fluctuation is the wave's amplitude, which determines how loud the sound is.
Of the five senses, hearing is probably the most important for our feeling of connection to the world around us. The sounds of our environment and the sounds of communication serve to link us to others in a way that vision alone cannot. We are submersed in our auditory world but we are only observers of our visual world. Sound provides the richness in our lives. Imagine a walk in the woods on a crisp autumn day. Hear the leaves crunching underfoot, the whisper of the wind in the trees, the honking of geese flying overhead, the laughter of children playing. We can close our eyes but our ears are always working. If the sounds around us begin to fade, we feel less a part of our world. Although people are quick to seek help for visual problems, hearing instrument use remains low despite great technological advances in the hearing healthcare field. Approximately 500 million people worldwide suffer from hearing loss.