The auditory system, also known as the hearing system, is the way you process and understand the sound around you. The auditory system allows each of us to take in the sounds around us, filter out what isn’t important (what we call background noise), and give meaning to what is important – like the sound of your alarm in the morning.
The auditory system has four parts. These parts are the outer, middle, and inner ear, and the auditory nervous system.
The ear canal and the pinna are the two parts of the outer ear. The pinna is the part of your ear that you can see. The ear canal is like a tube that moves sound from the outside of the ear toward the inside of the ear.
The middle ear consists of what we know as the eardrum, also called the tympanic membrane. It also contains three tiny bones – the stapes, incus, and malleus. These structures receive sound from the ear canal and keep it moving into the inner ear.
The inner consists of a spiral structure called the cochlea. The cochlea is lined with very small hairs. When sound waves reach the inner ear, the hairs in the cochlea send electrical signals to the auditory nerve. In the inner ear, sound is transformed into electricity- something the brain and the auditory nerve can understand.
The auditory nervous system consists of the auditory nerve and the auditory cortex of the brain. The auditory nerve carries electrical signals from the inner ear to the auditory cortex. In the auditory cortex, sounds are assigned meaning so you can make sense of what you hear.
The process of hearing involves all four parts of the auditory system described above. In order for your hearing to work normally, these steps have to happen. First, sound moves through the ear canal (outer ear) and hits the eardrum, causing it to wave back and forth.
Next, those sound waves move from the eardrum to the middle ear, where they hit the three tiny bones that sit there – the stapes, incus, and malleus. Then, the vibrations continue to the inner ear, where they hit the hairs that line the cochlea, the spiral structure. The tiny hairs send electrical signals to the auditory nerve when they vibrate.
The auditory nerve connects the inner ear to the auditory cortex and conveys the electrical signals from the hairs of the cochlea to the auditory cortex. In the brain, the information that the electrical signals carry is converted into a meaningful understanding of the sound you first heard. The brain allows us to make sense of the sound around us.
Hearing loss can occur from damage to any one of the parts of the auditory system. Damage to the outer and middle ear affects the ability of the ear to keep sound waves moving through the ear. Damage to the inner ear can affect the ability of the tiny hairs on the cochlea to convert sound waves into electrical signals that can be sent to the auditory nerve.
Damage to the auditory nerve is not common, but when it occurs, all of the information about the sounds you’re hearing never reach the brain. Damage to the auditory cortex, where the information about sound reaches its final destination, can result in an inability to make sense of the sounds you’re hearing.
For example, it may be difficult to detect tone of voice and where sound is coming from, and it may be hard to understand what people are saying. In rare cases, damage to the auditory cortex can result in deafness, even when other parts of the auditory system are intact.