While your ears are crucial to proper hearing, there’s another organ in your body that is just as important: your brain. The brain takes the soundwaves that enter the ears and translates them into words, music, and all the other noises that surround us each day, enabling us to experience sound. But how exactly does this happen?
Directing sound to the brain
Essentially, ears are complex pathways that capture, process, and transmit sound to the brain. The outer ear helps to funnel sound into the ear canal until it reaches the eardrum. These soundwaves cause the eardrum to vibrate, and the vibrations are sent to the ossicles (three tiny bones of the middle ear), which then amplify those vibrations and pass them along to the inner ear. When they reach the cochlea, tiny hair cells known as stereocilia react to the sound vibrations and transmit them into electrical signals captured by the auditory nerve. At this point, the brain takes over, and the magic of hearing really happens.
How the brain hears
The auditory nerve in each ear sends sound vibrations to the cochlear nucleus, one of two clusters in the brainstem. The cochlear nuclei process the sound information received and organize it according to pitch, duration, and intensity. Based on how the individual sounds are organized, they’re sent to different parts of the brain for further processing and interpretation.
The thalamus, at the base of the brain, also helps to process sound. In this part of the brain, sound is further analyzed to determine if there is any danger in what is heard, such as an alarm or someone screaming for help. If such a sound is detected, it triggers an emotional response—the fight or flight reflex.
The next stop is the auditory cortex, which enables us to understand a conversation. The role of the auditory cortex is to analyze time-varying signals in what the ears pick up, allowing us to perceive individual syllables and words, and thus process speech. It also works to recognize and identify other sounds, such as a musical instrument, and determine directionality and volume.
Other parts of the brain also play a role in how we interpret sound. For instance, the prefrontal cortex combines signals from the auditory cortex and other areas to help give sound meaning. This can include processing another person’s facial expressions along with the words they use, their tone when speaking, and our own emotions and memories, to give us a deeper understanding of the conversation and add more context to what we hear.
Helping your ears and your brain to hear
While the brain turns the vibrations sent through the ear into distinguishable sounds, hearing loss impedes on this process. If hearing loss is left untreated, sound signals can be missed or distorted, making it more difficult for the brain to translate those signals into meaningful sounds. However, when fitted with hearing aids, your ears can once again send the right signals to the brain, enabling you to properly hear, understand, and react to the soundwaves that enter your ears.