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How Do We Hear Sound?
Like most people, you probably take your hearing for granted. But have you ever wondered how you hear or how your auditory system captures, transmits and deciphers sound?
Your auditory system is one of your body’s most complex and delicate sensory systems. Your ears capture sound waves and convert them into electrical signals that travel to your brain. In the brain, these signals are decoded and interpreted as sounds.
The auditory system is incredibly sensitive and can detect a wide range of frequencies, from low-pitched rumbles to high-pitched whistles. It can also locate the source of a sound and filter out background noise. This complex system is constantly working to keep you attuned to your surroundings.
So next time you hear a sound, take a moment to appreciate the fantastic feat of hearing that is made possible by your auditory system.
Watch the video below to learn more about how hearing works.
How Does the Ear Work?
The ear is a fantastic organ that helps us to hear the world around us. It has three main parts:
- the outer ear
- the middle ear, and
- the inner ear.
Each part plays an essential role in the process of hearing.
The outer ear consists of the auricle or pinna, and ear canal. The auricle funnels sound waves into the ear canal, which amplifies the sound and directs it towards the eardrum.
The eardrum is a thin membrane that vibrates when struck by sound waves. These vibrations transmit to the inner ear through a series of tiny bones known as the ossicles.
The middle ear contains the ossicles, called the malleus, incus, and stapes, which are attached to the eardrum. The bones amplify sound waves and transmit them to the inner ear. In addition, the middle ear also contains two tiny muscles that help to protect the inner ear from loud noises.
The inner ear is responsible for converting vibrations into electrical impulses sent to the brain. This conversion occurs in the cochlea, a spiral structure filled with fluid and lined with thousands of tiny hair cells. As vibrations cause the liquid in the cochlea to ripple, the hair cells sway, and their movement triggers electrical impulses. These impulses travel along the auditory nerve to the brain, where they are interpreted as sound. The inner ear also contains the Eustachian tube.
The Eustachian tube is a small passage that connects the middle ear to the back of the nose. This tube helps equalize the pressure inside the ear and drains fluid from the middle ear. It’s lined with mucous membranes that produce secretions to help keep the eustachian tube clear. Abnormal or impaired function of the Eustachian tube may cause problems like ear infections and hearing loss.
The ear is an incredible organ that allows us to hear the world around us. By understanding how it works, we can better appreciate its importance in our lives.
Does Ear Shape Affect Hearing?
The shape of your outer ear does affect your hearing in several ways. The pinna or auricle is the fleshy part of your ear. Its shape is designed to amplify sounds, locate the source of a sound and filter background noise.
The outer ear is the part of the ear that is visible to us. The diagram below details the complex anatomy of the outer ear.
The outer ear plays a vital role in our ability to hear clearly. The function of the outer ear is to collect sound waves and direct them towards the eardrum. The shape of the outer ear helps to do this by funnelling sound waves into the ear canal.
The outer ear includes the external auditory canal, a tube that leads from the outer ear to the eardrum.
Tiny hairs line the ear canal to help to keep out dirt and other foreign objects. Earwax also forms a barrier against debris, foreign intruders and infection.
The shape of your ear also affects how well you hear high-pitched and low-pitched sounds. People with small ears usually have difficulty hearing high-pitched sounds, while people with prominent ears can hear low-pitched sounds better.
The angle of your ear also affects how well you hear. If your ear is pointing directly at the sound, you will hear it better than if your ear is turned away from the sound.
Finally, the size and shape of your ear canal also affect how well you hear. People with smaller ear canals often have difficulty hearing low-pitched sounds, while people with larger ear canals can hear high-pitched sounds better.
The 4 Parts of Your Auditory System
When we think of how hearing works, most of us only consider the three parts of the ear. There is a fourth part that is as equally critical in processing and interpreting sound, the brain.
The auditory system is the part of your body that enables you to hear. It consists of four main components:
- the outer ear
- the middle ear
- the inner ear, and
- the brain.
The outer ear is the visible part of the auditory system that extends outward from the head to the ear canal.
The middle ear is where the ear canal meets the eardrum. It contains three tiny bones (the incus, malleus, and stapes) that transmit sound vibrations from the eardrum to the inner ear.
The inner ear is a snail-shaped structure that contains the cochlear, a fluid-filled chamber that helps to amplify sound vibrations.
The brain is responsible for interpreting these sound vibrations and translating them into meaningful information.
Without all four parts working together, we would be unable to hear.
What Does the Cochlea Do?
The cochlea is a small, spiral-shaped organ in the inner ear. It is filled with fluid and lined with sensitive hair cells.
When sound waves enter the ear, they cause the fluid in the cochlea to ripple. This movement bends the hair cells, which triggers nerve impulses. These impulses travel to the brain, where they are interpreted as sound.
The hair cells of the cochlea are arranged in a series of loops, with each loop tuned to a specific frequency. This allows the ear to distinguish between different sounds, such as high-pitched and low-pitched noises.
The cochlea is also responsible for maintaining balance. Tiny crystals in the organ detect movement and send signals to the brain that help to keep you upright. Without it, you would constantly feel like you are falling over.
How Does Sound Travel Through the Ear to the Brain?
The external, middle and inner ears are all involved in transmitting sound to your brain.
The external ear consists of the auricle (pinna) and the ear canal. The outer ear canal ends at the eardrum (tympanic membrane), separating the external ear from the air-filled middle ear.
The Eustachian tube ventilates the middle ear, connecting the nasopharynx (the upper part of the throat connecting the nose and mouth).
Refer to the diagram below of the auditory pathway for the five stages of sound transmission to your brain.
- Acoustic pressure waves collected by the auricle pass through the external ear canal and cause vibrations in the drum membrane.
- These vibrations are transmitted to the middle ear bones, i.e., hammer (malleus), anvil (incus), and stirrup (stapes). The inner ear contains a coiled, fluid-filled tube that is named the cochlea. The cochlea is where the sound vibrations are transformed into a neural form. The organ of Corti in the cochlear duct contains hair cells that turn the vibrations into electric neural signals.
- The hair cells stimulate the auditory nerve (for hearing), which combines with the vestibular nerve (for balance), forming the vestibulocochlear nerve.
- The vestibulocochlear nerve (the eighth cranial nerve) transmits sound and equilibrium (balance) information from the inner ear to your brain.
- The auditory cortex processes and interprets sound.