How Many Sounds Can We Hear at Once?
Many of us with no hearing problems tend to take our hearing for granted. This is normal; we don’t always consider how we can see and hear, we just focus on what we’re hearing. However, the science of hearing and sound perception is a large field of study. There are hundreds of questions left unanswered, and we’re constantly learning more about how our brains and ears work together. Before we get into the specifics of how our brains process sound, we should have a firm understanding of what’s inside our ears, and how they work.
Human Ear Anatomy
Unlike our eyes and nose, the ear has a lot of moving parts. This makes them especially prone to problems, but it also showcases how the human body works in perfect tandem with itself. While we can’t see everything inside our ears, there’s a lot to learn about what lies within. Here’s a quick overview of the ear and its parts.
• Outer ear. This is the most visible part of your ear. While the shape and lack of flexibility make our ears seem primitive, they’re perfectly designed to funnel sound into our ears.
• Ear canal. This is the long walk that sound takes to reach our eardrum
• Tympanic membrane. Also known as the eardrum. This part divides the outer ear and the middle ear and vibrates when sounds are funneled into the ear.
• Ossicles. These are three small bones that move together to transmit sound. The malleus is the hammer, the incus the anvil, and the stapes the stirrup. They are suspended within your middle ear so they can transmit sound.
• Eustachian tube. This is a tube that connects your throat and ears. It keeps the pressure balanced in your middle ear so you can hear properly.
• Labyrinth. There are two labyrinths, the membranous and the bony. The bony labyrinth is located inside the membranous. The labyrinth contains three other organs: the cochlea, the vestibule, and the semicircular canals.
• Cochlea. This is a snail or spiral-shaped organ filled with fluid and lined with microscopic hairs. Vibrations stir these hair cells in different ways, allowing the brain to identify things like pitch and volume.
• Vestibule. This contains two sacks, known as the saccule and the utricle. They help maintain balance.
• Semicircular canals. Another organ dedicated to balance. The canals consist of three hollow loops; one senses horizontal movement, one senses vertical movement, and one senses tilt.
• Auditory nerve. Also known as the cochlear nerve. This transmits processed sound from the cochlea to the brain.
How the Ear Works
Now that we know every part of the ear, we can dig into how it works. Believe it or not, nearly every organ listed above has a vital role in how we hear. In fact, there are different types of hearing loss depending on which of these organs develops a problem. While our ears have evolved to work in perfect tandem, having so many parts creates a lot of room for things to go wrong. However, most people live their entire lives with some degree of hearing, so our ears do a good job of maintaining function.
When sound is transmitted, it travels through the air as a soundwave. That soundwave reaches our outer ear, where it is funneled down our ear canal and towards the eardrum. The tympanic membrane vibrates, which stirs the small bones (ossicles) in the middle ear. These bones amplify the vibrations and send them towards the cochlea.
Once these vibrations reach the cochlea, they are processed. Vibrations with high amplitude are processed as loud, while low amplitude vibrations are processed as quiet. The hair cells within the cochlea process pitch and nuance. Because the cochlea is shaped like a snail, some sounds resonate deeper inside the spiral. Nuanced sounds stimulate multiple parts of the cochlea at once. The cochlea does the hard work of processing sound into a readable format: brain signals. Sound from the ear to brain is transmitted via the auditory/cochlear nerve.
That brings us to the next step in understanding our hearing: pychoacoustics.
What Are Psychoacoustics?
In short, psychoacoustics refers to the relationship between sound and the brain. The brain handles sound perception and identification, which can be quite complex and variable. Sound can cause a physiological and psychological reaction, and psychoacoustics is dedicated to figuring out how and why our brain reacts to sounds. For example, have you ever gotten chills while listening to a musical score for no reason? That’s what psychoacoustics aims to understand: how and why we react to sound and music.
Psychoacoustics bring us to the big question: how many sounds can we hear at once? This is a loaded question, because it depends. In a room full of people, we are technically hearing all of their voices. They might jumble together into one big cloud of sound, but we are hearing all of them at once. However, psychoacoustics explores how we listen to sounds. While we might hear many sounds, we only listen to a few.
So, while we might be able to hear a ticking clock, someone’s footsteps, the wind blowing, a radio playing, a person humming along, and our own breathing, we are only listening to a few of these sounds. Our ears are constantly picking up on sounds, even if we don’t realise it. Psychoacoustics aims to explore what sounds activate thought and recognition, and how our brain reacts to the world around us. There’s a lot to learn, and we’re still trying to understand our brains and how we hear.
Did you learn something from this article? Signia Hearing puts out informational guides and blog posts every month, and all of them can help you get a better understanding of aural health, hearing loss, and hearing aids. There’s an entire library of information for you to explore, and you can stay updated on future posts by subscribing to our newsletter. There’s a lot to learn about how our ears work, and we’re trying to make that knowledge readily available to anyone who wants it.