As humans, we often take our abilities to interpret and interact with the world around with us for granted. An adult human has been using his body to sense and feel the world around him longer than he can remember. Our bodies react to the world around us automatically, but it can be refreshing to step back and take at look at how our senses work. One of the most mysterious things that our bodies sense is sound. Sound allows us to communicate with each other, providing our bodies with important information about its surroundings, and even invokes emotion through music – but what is sound and how do we use it?

If you've ever stood near a large sound system or put your finger up to the speaker cone of a small one, you will not be surprised to find that sound has to do with vibration. All sounds are created by the vibrations of an object, or sound source. Almost anything can vibrate enough to create sound. Two billiard balls cause a vibration as they hit together, for example. The force of the impact of one ball against another causes them both to vibrate quickly for a short amount of time, which in turn causes the air around them to vibrate.

The air is a much different substance than a solid, and an interesting thing begin to happen as air vibrates. The vibrations push and pull against air particles to form waves that travel away from the source. As a sound moves through the air the vibrations become weaker, just like a ball ever slows to a stop when thrown. If a sound reaches the ear before it dissipates strictly, delicate portions inside the ear absorb the vibration. The brain can tell how loud the sound is by how much the ear is vibrating. Ears are sensitive, however, and can be damaged by intense vibrations. People exposed to loud sounds regularly can get permanent damage detected by a hearing test.

Aside from the loudness of a noise, there are other characteristics of sound that help humans distinguishing between them. A sound's frequency determines the pitch of the sound and is determined by how quickly it vibrates. A sound's timbre is caused by little irregularities in the sound waves. Timbre provides uniqueness to similar sounds, like the slight differences between each human voice.

Over time, the human ear naturally loses the ability to absorb certain vacancies. A simple hearing test can show what frequencies an ear can still process. The inner ear is very sensitive and may become less effective if abused. A damaged ear has a hard time picking up quieter sounds and also has trouble distinguishing between timbres. A hearing test can determine the amount of the damage, but there is no current way to repair it.

As sound plays a critical role in human sensing, it's important to take care of the ear. Since vibrations become softer the farther you are from a sound source, you'll want to keep a safe distance from noises that are too loud. If you're concerned that you have sustained some damage, a hearing test can tell you the amount, help identify what has caused it, and how to avoid further damage. You only get one pair of ears, so treat them well!