What Is Sound?
To understand how hearing works, you first have to understand sound. Your hearing system is based solely on physical movement. 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.
How Hearing Works
To hear sound, your ear has to do three basic things:
- Direct the sound waves into the hearing part of the ear
- Sense the fluctuations in air pressure
- Translate these fluctuations into an electrical signal that your brain can understand
Once the sound waves travel into the ear canal, they vibrate the tympanic membrane, commonly called the eardrum. The eardrum is a thin, cone-shaped piece of skin, about 10 millimeters (0.4 inches) wide. Since air from the atmosphere flows in from your outer ear as well as your mouth, the air pressure on both sides of the eardrum remains equal. This pressure balance lets your eardrum move freely back and forth. The compressions and rarefactions of sound waves push the drum back and forth. Higher-pitch sound waves move the drum more rapidly, and louder sound moves the drum a greater distance.
Built In Hearing Protection
The eardrum can also serve to protect the inner ear from prolonged exposure to loud, low-pitch noises. When the brain receives a signal that indicates this sort of noise, a reflex occurs at the eardrum. The tensor tympani muscle and the stapedius muscle suddenly contract. This pulls the eardrum and the connected bones in two different directions, so the drum becomes more rigid. When this happens, the ear does not pick up as much noise at the low end of the audible spectrum, so the loud noise is dampened.
In addition to protecting the ear, this reflex helps you concentrate your hearing. It masks loud, low-pitch background noise so you can focus on higher-pitch sounds. Among other things, this helps you carry on a conversation when you’re in a very noisy environment, like a rock concert. The reflex also kicks in whenever you start talking—otherwise, the sound of your own voice would drown out a lot of the other sounds around you.
The Idea Behind Noise Reduction Headphones
Our noise reduction headphones try to further reduce noise by increasing the isolation of your eardrum from sound. The only way to reduce noise is by reducing the amount your eardrum vibrates. Our headphones have been carefully and technically designed with state of the art sound blocking materials. Most noise cancellation headphones today try to reshape the noise as it hits your ear. Our headphones actually block the sound from reaching your ear by reflecting the sound vibrations away from you. That is why our headphones reduce more noise than any other headphones available.